rounds: + Codeforces Round 907 (Div. 2), which has a *2000 problem as Div2F :)
+ CodeforcesRound 880, Out of these $10$ rounds, $4$ rounds are generally considered as good rounds,
$3$ rounds have
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You can use several words in query to find by all of them at the same time. In addition, if you are lucky search understands word forms and some synonyms. It supports search by title and author. Examples:
305— search for 305, most probably it will find blogs about the Round 305andrew stankevich contests— search for words "andrew", "stankevich" and "contests" at the same timeuser:mikemirzayanov title:testlib— search containing "testlib" in title by MikeMirzayanov"vk cup"— use quotes to find phrase as istitle:educational— search in title
Results
1.
Goodbye 74TrAkToR + Problem A~E: The problems themselves are good and typical A~E. Indeed I like problem D. The pretest for A is a bit weak, and it's not a big problem yet.
+ Problem F: The problem has an origin. :) See the link: [click](https://www.luogu.com.cn/problem/P9394). The problem in contest is only a weakened version of the one in Luogu.
+ Problem G: It's said that our great coordinator had not proved the time complexity of the intended solution is correct :) If the authors did, please share it in the editorial. (although this problem is completely beyond my ability :) )
+ Problem H: Oh dear [user:74TrAkToR,2023-12-30], could you please OEIS the sequence before you use the "several-integer-input" problem in
rounds next time? Anyone who copied the first example and opened [https://oeis.org/A286331](https://oeis.org/A286331) could quickly get the formula. And the problem itself is not so hard imo. Anyway, it should not be used in contest, especially for the last problem.
For me pers...
2.
Educational Codeforces Round 121 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1626] [contest:1626] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-01-15] Dalabaev, Vladimir [user:vovuh,2022-01-15] Petrov, Ivan [user:BledDest,2022-01-15] Androsov, Mak...
Educational Codeforces Round 121 [Rated for Div. 2], Educational Codeforces Round 121 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1626] [contest:1626] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 121 (Rated for Div. 2)
3.
How to set a Div. 1 or a Div. 2 round on Codeforces As you probably know, most of the rounds on Codeforces are created by active community members. We are very grateful to our talented authors from all around the world for bringing their ideas to tens of thousands of competitors, providing fun and learning experience for contestants of every expertise, from beginners to the world's top programmers. This post will cover the steps you need to take propose a round and become a problem writer on Codeforces.
## Who can be a problem author
Best problems usually come from the most experienced participants. We have limited resources for rounds reviewing, so to make the process flawless for writers, starting January 1st, 2021, the following requirements for problem authors will be applied:
- rating: 2100 or above, or
- was a writer in the past.
The restrictions may be updated in the future, the post will be updated accordingly. If your round is already in the review status, don't worry, it will be reviewed regardless of the current...
How to set a Div. 1 or a Div. 2 round on Codeforces, propose a round and become a problem writer on Codeforces. ## Who can be a
problem author Best
4.
Codeforces Round 1037 (Div. 3) Hello, Codeforces!
I am very excited to invite you to our contest [contest:2126], which starts on [contest_time:2126]. You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
The problems were authored by me, [user:__rose,2025-07-15], [user:Pishka12,2025-07-15], [user:Chalishkan,2025-07-15] and [user:I_HATE_MD_DM,2025-07-15] to solve and alter them.
The round will be hosted by the rules of educational rounds (extended **ICPC**). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a **12-hour phase** of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution — rank will be determined by number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of 10 minutes, following the rules of educational rounds.
[Remember](https://mirror.codeforces.com/blog/entry/59228) that only t...
Codeforces Round 1037 (Div. 3), The round will be hosted by the rules of educational rounds (extended
**ICPC**). Thus, all, ], [user:Chalishkan,2025-07-15] and [user:I_HATE_MD_DM,2025-07-15] to solve and
alter them. Theround will
Announcement of Codeforces Round 1037 (Div. 3)
5.
Codeforces: Results of 2019 <a style="float:right; display: inline-block; margin:0 1em 1em 2em; max-width: 60%;" href="https://codeforces.me/10years"/>
<img style="max-width:100%" src="https://assets.codeforces.com/images/codeforces-10-years-300.png"/>
</a>
Hi Codeforces!
The platform recently turned 10 years old. We accept your congratulations at <a href="https://codeforces.me/10years">https://codeforces.me/10years</a>.
Please review the progress in 2019 and support the anniversary crowdfunding campaign. Your donation will be a contribution to the future of Codeforces, will
help its development and work. We need resources to continue to host rounds, not to stop developing,
to innovate and to maintain the existing infrastructure.
In 2019, together with numerous writers the coordinators worked on problems: [user:KAN,2020-02-06], [user:300iq,2020-02-06], [user:cdkrot,2020-02-06], [user:arsijo,2020-02-06] and recently joined [user:isaf27,2020-02-06]. And this year,
rounds coordinated by other exper...
/codeforces-10-years-300.png"/> Hi Codeforces! The platform recently turned 10
years old. We
6.
Codeforces Round 1034 (Div. 3) Hello, Codeforces!
==================
I am very excited to invite you to my first-ever contest, [contest:2123], which will start on [contest_time:2123]! In this contest, you will be given **2 hours and 15 minutes** to solve **7 problems**.
The round will be hosted by the rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution — rank will be determined by number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of **10 minutes**, following the rules of educational rounds.
[As a reminder](https://codeforces.me/blog/entry/59228), only trusted participants of the third division will be included in the official standings table. This is a compulsory measure for combating unspo...
Codeforces Round 1034 (Div. 3), and 15 minutes** to solve **7 problems**. The round will be hosted by the
rules ofeducational, The round will be hosted by the rules of educational rounds (extended ICPC).
Thus, all solutions
Announcement of Codeforces Round 1034 (Div. 3)
7.
Educational Codeforces Round 90 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1373] [contest:1373] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-06-24] Glazov, Adilbek [user:adedalic,2020-06-24] Dalabaev, Vladimir [user:vovuh,2020-06-24] Petrov, Ivan [us...
Educational Codeforces Round 90 [Rated for Div. 2], Educational Codeforces Round 90 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1373] [contest:1373] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 90 (Rated for Div. 2)
8.
Codeforces Round 1042 (Div. 3) Hello Codeforces!
We are glad to invite you to participate in [contest:2131], which will start on [contest_time:2131]. You will be given **2 hours and 15 minutes** to solve **8** problems.
The problems are authored and prepared by [user:-firefly-,2025-08-07], [user:efishel,2025-08-07], [user:Tobo,2025-08-07], and [user:__baozii__,2025-08-07].
The round will be hosted by the rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution — rank will be determined by number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of **10 minutes**, following the rules of educational rounds.
[As a reminder](https://codeforces.me/blog/entry/59228), only trusted participants of the th...
Codeforces Round 1042 (Div. 3), ; wrong submissions will incur the usual penalty of **10 minutes**, following
the rules ofeducational, The round will be hosted by the rules of educational rounds (extended ICPC).
Thus, all solutions
Announcement of Codeforces Round 1042 (Div. 3)
9.
Codeforces Round #547 (Div. 3) Hello, Codeforces!
I am pleased to invite you to [contest:1141], which will start on [contest_time:1141]. Everyone whose current rating is strictly less than 1600 is invited to participate officially. All others can take part out of the competition.
It so happened that the schedule of this month is not replete with rounds (coordinators, we hope for you!). Therefore I decided to partially correct the situation. All the problems of this round were invented and prepared by me on the last day of [Hello Muscat Programming Bootcamp 2019] (/blog/entry/63298) and on flights from Muscat to St. Petersburg. I even specially noted the time for preparation: for the current moment (the problems are ready for testing) I spent about 6 hours on their preparation, including inventing some of the problems. I really like working on problems, this is something at the intersection of creativity and programming. I really hope you enjoy the result of my work.
<center>
<br/>
<img src = "/predownload...
Codeforces Round #547 (Div. 3), problems for the round. The round will be hosted by rules of educational
Announcement of Codeforces Round 547 (Div. 3)
10.
Codeforces Round 1065 (Div. 3) <img src="https://c.tenor.com/G25fbL0QjmYAAAAd/tenor.gif" style="width: 400.0px;float: right;margin: 0 1.0em 1.0em 1.0em;max-width: 100.0%;max-height: 100.0%;">
Hello, Codeforces!
==================
I am very excited to invite you to my second-ever contest, [contest:2171], which will start on [contest_time:2171]! In this contest, you will be given **2 hours and 30 minutes** to solve **7 problems, two of which have been split into subtasks**. The subtasks for a given problem are not necessarily placed adjacently in the problemset.
The round will be hosted by the rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution — rank will be determined by number of problems solved, followed by penalty; wrong submissions...
Codeforces Round 1065 (Div. 3), necessarily placed adjacently in the problemset. The round will be hosted by
the rules ofeducational, The round will be hosted by the rules of educational rounds (extended ICPC).
Thus, all solutions
Announcement of Codeforces Round 1065 (Div. 3)
11.
Educational Codeforces Round 91 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1380] [contest:1380] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-07-11] Glazov, Adilbek [user:adedalic,2020-07-11] Dalabaev, Vladimir [user:vovuh,2020-07-11] Petrov, Ivan [us...
Educational Codeforces Round 91 [Rated for Div. 2], Educational Codeforces Round 91 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, **UPD:** The contest is delayed by 10 minutes., **UPD:** Контест отложен на 10 минут., Hello Codeforces! On [contest_time:1380] [contest:1380] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 91 (Rated for Div. 2)
12.
Codeforces Round 1071 (Div. 3) Hello, Codeforces!
==================
[user:iceborworntat,2025-12-19], [user:nortglg,2025-12-19], [user:omsincoconut,2025-12-19], and I are excited to invite everyone to [contest:2179], which will take place on [contest_time:2179]. You will be offered **8 problems**, and you will be given **2 hours and 30 minutes** to solve them.
Please note that this contest contains **at least one interactive problem** and **at least one run-twice problem**. Please read the guides for [interactive problems](https://codeforces.me/blog/entry/45307) and [run-twice problems](https://codeforces.me/blog/entry/147996) before the contest if you are unfamiliar with them.
The round will be hosted by the rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there i...
Codeforces Round 1071 (Div. 3), ; wrong submissions will incur the usual penalty of **10 minutes**, following
the rules ofeducational, The round will be hosted by the rules of educational rounds (extended ICPC).
Thus, all solutions
Announcement of Codeforces Round 1071 (Div. 3)
13.
Educational Codeforces Round 100 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1463] [contest:1463] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-12-16] Glazov, Adilbek [user:adedalic,2020-12-16] Dalabaev, Vladimir [user:vovuh,2020-12-16] Petrov, Ivan [us...
Educational Codeforces Round 100 [Rated for Div. 2], Educational Codeforces Round 100 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1463] [contest:1463] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 100 (Rated for Div. 2)
14.
Educational Codeforces Round 89 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1366] [contest:1366] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-06-10] Glazov, Adilbek [user:adedalic,2020-06-10] Dalabaev, Vladimir [user:vovuh,2020-06-10] Petrov, Ivan [us...
Educational Codeforces Round 89 [Rated for Div. 2], Educational Codeforces Round 89 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1366] [contest:1366] will start. Series of
Educational, The problems were invented and prepared by Roman [user:Roms,2020-06-10] Glazov,
Adilbek, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Задачи вместе со мной придумывали и готовили Роман [user:Roms,2020-06-10]
Глазов, Адилбек
Announcement of Educational Codeforces Round 89 (Rated for Div. 2)
15.
Educational Codeforces Round 196 [rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 150px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of [Neapolis University Pafos](https://www.nup.ac.cy/).
[contest:2283] will start on [contest_time:2283].
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them. I hope everyone participating finds interesting problems for them to solve.
I would like to express my gratitude to [user:MikeMirzayanov,2026-10-12] for creating Codeforces and Polygon ...
Educational Codeforces Round 196 [rated for Div. 2], Educational Codeforces Round 196 [рейтинговый для Div. 2], ! The series of Educational Rounds continues thanks to the support of [Neapolis
University Pafos, I would like to express my gratitude to [user:MikeMirzayanov,2026-10-12] for
creating Codeforces, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Я бы хотел поблагодарить Михаила [user:MikeMirzayanov,2026-10-12] Мирзаянова за
платформы
Announcement of Educational Codeforces Round 196 (Rated for Div. 2)
16.
Educational Codeforces Round 93 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1398] [contest:1398] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-08-13] Glazov, Adilbek [user:adedalic,2020-08-13] Dalabaev, Vladimir [user:vovuh,2020-08-13] Petrov, Ivan [us...
Educational Codeforces Round 93 [Rated for Div. 2], Educational Codeforces Round 93 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1398] [contest:1398] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 93 (Rated for Div. 2)
17.
Educational Codeforces Round 7 Hello, Codeforces!
Educational Codeforces Round 7 will take place on [10 February 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+7&iso=20160210T1500) for the first and second divisions. You can read about educational rounds [here](http://codeforces.me/blog/entry/21496) and [here](http://codeforces.me/blog/entry/21565).
\<This paragraph was modified last time\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
\</This paragraph was modified last time\>
Thanks a lot to Aleksa Plavsic [user:allllekssssa,2016-02-08] who suggested the problems D, E and Ivan Po...
Educational Codeforces Round 7, /fixedtime.html?msg=Educational+Codeforces+Round+7&iso=20160210T1500) состоится
седьмой учебный раунд, =Educational+Codeforces+Round+7&iso=20160210T1500) состоится седьмой учебный
раундEducational Codeforces
Announcement of Educational Codeforces Round 7
18.
Codeforces Round 1029 (Div. 3) أهلاً, Codeforces!
----------------------
[user:cry,2025-06-04], [user:Intellegent,2025-06-04], and I are really excited to invite you to participate in [contest:2117], which will take place on [contest_time:2117]. You will be given $2$ hours and $15$ minutes to solve $8$ problems.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of **10 minutes** for each wrong submission, following the rules of educational rounds.
Note that the penalty for each wrong submission in this round is **10 minutes**. Also, **note the rule [restricting AI use](https://codeforces.me/blog/entry/133941)**. If you are caught using AI in an unorthodox manner, you will be sent to [use...
Codeforces Round 1029 (Div. 3), submission in this round is **10 minutes**. Also, **note the rule [restricting
AI use](https, The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1029 (Div. 3)
19.
Codeforces Round #764 (Div. 3) Hello! [contest:1624] will start at [contest_time:1624]. You will be offered 7-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **7-8 problems** and **2 hours and 15 minutes** to solve them. One of the problems in this round is **interactive**. Don't forget to read the [guide on interactive problems](https://codeforces.me/blog/entry/45307).
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official s...
Codeforces Round #764 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus
Announcement of Codeforces Round 764 (Div. 3)
20.
Educational Codeforces Round 96 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1430] [contest:1430] will start. **Note that the start time is unusual**.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2020-10-10] Dalabaev, Alex [user:fcspartakm,2020-10-10] Frolov an...
Educational Codeforces Round 96 [Rated for Div. 2], Educational Codeforces Round 96 [рейтинговый для Div. 2], is unusual**. Series of Educational Rounds continue being held as
[Harbour.Space University, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, посылки, являющейся полным решением, равен 10 минутам. После окончания раунда
будет период времени, > A [user:Sevlll, 2020-10-12] 0:01 B, >A [user:Sevlll, 2020-10-12] 0:01 B, >[user:ViciousCoder, 2020-10-12] 100:-9, The problems were invented and prepared by Adilbek [user:adedalic,2020-10-10]
Dalabaev, Alex, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, [user:WZYYN, 2020-10-12] 7 186 2, Задачи вместе со мной придумывали и готовили Адилбек [user:adedalic,2020-10-10]
Далабаев и
Announcement of Educational Codeforces Round 96 (Rated for Div. 2)
21.
Div. 2 C's are NOT getting easier Recently, after like every Div. 2 contest I see some blogs/comments saying that ~2C problems are getting easier. What's the evidence? They say these problems have _many_ solves.
No, I think it's the opposite.
Definite number of solves is not a good measure for evaluating the difficulty. A not too precise, but statistically more reliable way to evaluate the difficulty of a 2C problem would be calculating `(# of official solves on C) / (# of official solves on A)`, assuming that most people have always been able to solve 2A.
Let's calculate them for recent 10 Div. 2-only contests' (not counting Educational rounds) C problems:
- [contest:1993] : 6755/19951 (33.86%)
- [contest:1995] : 2384/13980 (17.05%)
- [contest:1990] : 3490/11867 (29.41%)
- [contest:1988] : 7239/12234 (59.17%)
- [contest:1983] : 5504/16414 (33.53%)
- [contest:1982] : 7654/14965 (51.15%)
- [contest:1978] : 5115/12031 (42.52%)
- [contest:1979] : 9051/17663 (51.24%)
- [contest:1981] : 1128/10942 (10.31...
Let's calculate them for recent 10 Div. 2-only contests' (not counting
Educational rounds) C
22.
Sums and Expected Value — part 1 part 2: https://codeforces.me/blog/entry/62792
Watch my lecture-stream tomorrow (Thursday) at [14:00 CEST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=EV+lecture+1&iso=20181025T14&p1=262) — <s>[https://www.youtube.com/watch?v=qdlPY37MBPo](https://www.youtube.com/watch?v=qdlPY37MBPo)</s> [https://www.youtube.com/watch?v=U_h3IjreRek](https://www.youtube.com/watch?v=U_h3IjreRek).
I will go through theory and problems from this blog.
The only prerequisite is knowing what is probability.
The next (harder) part on Monday.
The video will be available later, with timestamps for each problem — so you don't have to watch everything.
### Definition of EV
Let's say we bought a lottery ticket for 2$.
We will win 10$ with probability 10%, and 20$ with p-bility 2%.
On average, it gives us $0.1 \cdot 10 + 0.02 \cdot 20 = 1.4$,
so we are worse off after buying the ticket.
The computed average is called the expected value.
The expected value (EV, expecta...
+7$. 5. **Imbalanced array (CF Educational Round 23)** Same as the previous
problem, but choose a
23.
Educational Codeforces Round 10 Hello, Codeforces!
[Note the unusual (for the educational round) start time!]
Educational Codeforces Round 10 will take place after a long delay on [25 march 2016 at 16:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+10&iso=20160325T1300) for the first and the second divisions. The long delay is caused by the high frequency of contests and championships on Codeforces. You can read about educational rounds [here](http://codeforces.me/blog/entry/21496) and [here](http://codeforces.me/blog/entry/21565).
\<The same as before\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to m...
Educational Codeforces Round 10, /fixedtime.html?msg=Educational+Codeforces+Round+10&iso=20160325T1300) после
продолжительного перерыва, ://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+
Round+10&iso=20160325T1300) for the, =Educational+Codeforces+Round+10&iso=20160325T1300) после продолжительного
перерыва состоится очередной, The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will, [Note the unusual (for the educational round) start time!]
Announcement of Educational Codeforces Round 10
24.
Educational Codeforces Round 97 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1437] [contest:1437] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-10-26] Glazov, Adilbek [user:adedalic,2020-10-26] Dalabaev, Vladimir [user:vovuh,2020-10-26] Petrov, Ivan [us...
Educational Codeforces Round 97 [Rated for Div. 2], Educational Codeforces Round 97 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, > A [user:Drew_is_me, 2020-10-27] 0:01 , >A [user:Drew_is_me, 2020-10-27] 0:01 B, Hello Codeforces! On [contest_time:1437] [contest:1437] will start. Series of
Educational, The problems were invented and prepared by Roman [user:Roms,2020-10-26] Glazov,
Adilbek, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, [user:Um_nik, 2020-10-27] 7 149 , Задачи вместе со мной придумывали и готовили Роман [user:Roms,2020-10-26]
Глазов, Адилбек
Announcement of Educational Codeforces Round 97 (Rated for Div. 2)
25.
Educational Codeforces Round 88 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1359] [contest:1359] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-05-27] Glazov, Adilbek [user:adedalic,2020-05-27] Dalabaev, Vladimir [user:vovuh,2020-05-27] Petrov, Ivan [us...
Educational Codeforces Round 88 [Rated for Div. 2], Educational Codeforces Round 88 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1359] [contest:1359] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 88 (Rated for Div. 2)
26.
Educational Codeforces Round 85 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1334] [contest:1334] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-04-09] Glazov, Adilbek [user:adedalic,2020-04-09] Dalabaev, Vladimir [user:vovuh,2020-04-09] Petrov, Ivan [us...
Educational Codeforces Round 85 [Rated for Div. 2], Educational Codeforces Round 85 [рейтинговый для Div. 2], for the next Educational Round, a space in a course of your choice from our
Computer Science or Data, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, специальный приз для следующего Educational Round, место на курсе по вашему
выбору из наших программ по, > A [user:Isabella_Vesterbury, 2020-04-10] 0:02 , >A [user:Isabella_Vesterbury, 2020-04-10] 0:02 , >[user:greencis, 2020-04-10] 174:-53, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, [user:MiFaFaOvO, 2020-04-10] 7 153
Announcement of Educational Codeforces Round 85 (Rated for Div. 2)
27.
Educational Codeforces Round 92 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1389] [contest:1389] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-07-28] Glazov, Adilbek [user:adedalic,2020-07-28] Dalabaev, Vladimir [user:vovuh,2020-07-28] Petrov, Ivan [us...
Educational Codeforces Round 92 [Rated for Div. 2], Educational Codeforces Round 92 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, -29] 10:-10, Hello Codeforces! On [contest_time:1389] [contest:1389] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 92 (Rated for Div. 2)
28.
Codeforces Round 1080 (Div. 3) Oh hello there. I, [user:chromate00,2026-02-14], am back! Oh no, I hope you are not misunderstanding me, I'm not pulling a joke on the announcement this time. I'm too busy for that right now. So here's the <strike>(mostly copy-pasted)</strike> announcement of [contest:2195].
Anyways. Starting from [contest_time:2195], you will be given **$\mathbf{7}$ or $\mathbf{8}$ problems** to be solved in **$\mathbf{2.5}$ hours**.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of **10 minutes** for each wrong submission, following the rules of educational rounds.
[Remind](https://codeforces.me/blog/entry/59228) yourself that only the trusted participants of the third ...
Codeforces Round 1080 (Div. 3), The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1080 (Div. 3)
29.
Codeforces Round 1096 (Div. 3) Hello, Codeforces!
------------------
I am super excited to invite you to participate in [contest:2227], which will take place on [contest_time:2227]. You will be given $2$ hours and $30$ minutes to solve $8$ problems. All problems were authored and prepared by me.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of **10 minutes** for each wrong submission, following the rules of educational rounds.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as...
Codeforces Round 1096 (Div. 3), to solve $8$ problems. All problems were authored and prepared by me. The round
will be hosted, The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1096 (Div. 3)
30.
Codeforces Round 1020 (Div. 3) <center>
<h1> Hello, Codeforces! </h1>
</center>
[user:cry,2025-04-19] and I are _very very very_ excited to invite you to participate in [contest:2106], which will take place on [contest_time:2106]. You will be given **7 problems** and **2 hours & 15 minutes** to solve them. There will be **at least one** interactive problem, so please make sure to read [this guide](https://codeforces.me/blog/entry/45307) if you are not familiar with the format. One of the problems will be split into two subtasks.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of **10 minutes** for each wrong submission, following the rules of educational rounds.
[Remind](https://codef...
Codeforces Round 1020 (Div. 3), The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1020 (Div. 3)
31.
Codeforces Round #1125 (Div. 3) Hello! We invite you to participate in [contest:2275], which will take place on [contest_time:2275].
This will be a Division 3 round. You will be given **8 problems**, authored by me and polished to perfection with the help of [user:Noobish_Monk,2026-09-30] and [user:Gornak40,2026-09-30], as well as **2 hours and 30 minutes** to solve them.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of **10 minutes** for each wrong submission, following the rules of educational rounds.
We [remind you](https://codeforces.me/blog/entry/59228) that only *trusted participants of the third division* will be included in the official standings. This is a necessary measure to...
Codeforces Round #1125 (Div. 3), well as **2 hours and 30 minutes** to solve them. The round will be hosted by
rules ofeducational, The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1125 (Div. 3)
32.
Educational Codeforces Round 103 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1476] [contest:1476] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-01-28] Glazov, Adilbek [user:adedalic,2021-01-28] Dalabaev, Vladimir [user:vovuh,2021-01-28] Petrov, Ivan [us...
Educational Codeforces Round 103 [Rated for Div. 2], Educational Codeforces Round 103 [рейтинговый для Div. 2], ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением,
равен10 минутам, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, > [user:WZYYN, 2021-01-29] 0:10 D , >98:-10 , >[user:WZYYN, 2021-01-29] 0:10 D , Hello Codeforces! On [contest_time:1476] [contest:1476] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 103 (Rated for Div. 2)
33.
Codeforces Round #656 (Div. 3) <too-old-joke-about-copy-paste>
Hello!
[contest:1385] will start at [contest_time:1385]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included i...
Codeforces Round #656 (Div. 3), rules of educational rounds (extended ACM-ICPC). Thus, during the round,
solutions will be judged on
Announcement of Codeforces Round 656 (Div. 3)
34.
Educational Codeforces Round 101 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1469] [contest:1469] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-12-27] Glazov, Adilbek [user:adedalic,2020-12-27] Dalabaev, Vladimir [user:vovuh,2020-12-27] Petrov, Ivan [us...
Educational Codeforces Round 101 [Rated for Div. 2], Educational Codeforces Round 101 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1469] [contest:1469] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 101 (Rated for Div. 2)
35.
Educational Codeforces Round 110 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1535] [contest:1535] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-06-03] Glazov, Adilbek [user:adedalic,2021-06-03] Dalabaev, Vladimir [user:vovuh,2021-06-03] Petrov, Ivan [us...
Educational Codeforces Round 110 [Rated for Div. 2], Educational Codeforces Round 110 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1535] [contest:1535] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 110 (Rated for Div. 2)
36.
Educational Codeforces Round 31 Hello Codeforces!
On [October 27, 17:05 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=27&month=10&year=2017&hour=17&min=5&sec=0&p1=166) Educational Codeforces Round 31 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.me/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-10-26] Androsov, Vladimir [user:0n25,2017-10-26] Petrov, Alexey [user:Perforator,2017-10-26] Ripinen, Mike [user:MikeMirzayanov,2017-10-26] ...
Educational Codeforces Round 31, /fixedtime.html?day=27&month=10&year=2017&hour=17&min=5&sec=0&p1=166) начнётся
Educational Codeforces Round
Announcement of Educational Codeforces Round 31
37.
Educational Codeforces Round 30 Hello Codeforces!
On [October 12, 17:05 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=12&month=10&year=2017&hour=17&min=5&sec=0&p1=166) Educational Codeforces Round 30 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.me/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-10-11] Androsov, Vladimir [user:0n25,2017-10-11] Petrov, Mike [user:MikeMirzayanov,2017-10-11] Mirzayanov and me.
Good luck to all partic...
Educational Codeforces Round 30, /fixedtime.html?day=12&month=10&year=2017&hour=17&min=5&sec=0&p1=166) начнётся
Educational Codeforces Round
Announcement of Educational Codeforces Round 30
38.
Invitation to Codeforces Round 962 (Div. 3) <center> Hewwo Cowodeforcers!
------------------
</center>
[user:sum,2024-07-04] and I are overjoyed to welcome you to participate in [contest:1996] on [contest_time:1996]. This contest is the last stop on our mission to problemset for every division. We hope you've been enjoying our stuff so far!
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**. After open hacks all accepted solutions will be rejudged on successful hacks.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for each wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsp...
Invitation to Codeforces Round 962 (Div. 3), far! The round will be hosted by rules of educational rounds (extended ICPC).
Thus, solutions
Announcement of Codeforces Round 962 (Div. 3)
39.
Codeforces Round 1122 (Div. 3) ## Hello, Codeforces!
I am very excited to invite you to participate in [contest:2266], which will take place on [contest_time:2266]. You will be given $2$ hours and $30$ minutes to solve $7$ or $8$ problems. All problems were authored and prepared by me, [user:WorldWarV,2026-09-16].
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of $10$ minutes for each wrong submission, following the rules of educational rounds.
You should [remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsport...
Codeforces Round 1122 (Div. 3), The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1122 (Div. 3)
40.
Educational Codeforces Round 152 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1849] [contest:1849] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours to solve them**.
The problems were invented and prepared by Adilbek [user:adedalic,2023-07-26] Dalabaev, Mikhail [user:awoo,2023-07-26] Piklyaev, Maksim [user:Neon,2023-07-26] Mescheryakov and ...
Educational Codeforces Round 152 [Rated for Div. 2], Hello Codeforces! On [contest_time:1849] [contest:1849] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 152 (Rated for Div. 2)
41.
Codeforces Round 1084 (Div. 3) Hello, Codeforces!
==================
I am exhilarated to invite you to participate in [contest:2200], which will be held on [contest_time:2200]! You will be given $7$-$8$ problems to solve in $2$ hours and $15$ minutes. All problems were authored and prepared by me.
The round will be hosted by rules of educational rounds (extended ICPC). During the round, all solutions will be judged on preliminary tests. After the round, there will be a 12-hour phase of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. There will also be the usual penalty of 10 minutes for each wrong submission.
[As a reminder](https://codeforces.me/blog/entry/59228), only trusted participants of the third division will be included in the official standings table. This is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:
- participate in at least five rated rounds (and solve at leas...
Codeforces Round 1084 (Div. 3), The round will be hosted by rules of educational rounds (extended ICPC). During
theround, all
Announcement of Codeforces Round 1084 (Div. 3)
42.
Educational Codeforces Round 163 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
We are pleased to announce a new long-term partnership between Codeforces and [Neapolis University Pafos](https://www.nup.ac.cy/). Now educational rounds will be supported by Neapolis University Pafos. Stay tuned and you will find out more soon.
On [contest_time:1948] [contest:1948] will start.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user...
Educational Codeforces Round 163 [Rated for Div. 2], Educational Codeforces Round 163 [рейтинговый для Div. 2], Pafos](https://www.nup.ac.cy/). Now educational rounds will be supported by
Neapolis University Pafos, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 163 (Rated for Div. 2)
43.
Codeforces Round 1107 (Div. 3) #### Hello Codeforces!!!
I am more than happy to invite you to my first solo round [Codeforces Round 1107 (Div. 3)](https://codeforces.me/contest/2241), which starts on [contest_time:2241]. You will be given $7$ problems and $2$ hours $15$ minutes to solve them.
All the problems were authored and prepared by me.
The round will be hosted by the rules of educational rounds (extended <b>ICPC</b>). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a <b>12-hour phase</b> of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution — rank will be determined by the number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of 10 minutes, following the rules of educational rounds.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will...
Codeforces Round 1107 (Div. 3), The round will be hosted by the rules of educational rounds (extended ICPC).
Thus, all
Announcement of Codeforces Round 1107 (Div. 3)
44.
Educational Codeforces Round 170 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/). They offer a BSc in Computer Science and AI with [JetBrains Scholarships] (https://lp.jetbrains.com/academy/csai-program/). Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Curious? Check out the [CSAI curriculum] (https://drive.google.com/file/d/19I776O8NG07ie2Q14wwBspuh3De4kbHc/view) now. Limited scholarships available — don't miss your chance to study in Europe for free!
Are you looking to sharpen your skills and increase your chances of getting a scholarship? Join the free clubs for high school students from JetBrains:
- [Math club](https://lp.jetbrains.com/youth-math-club/)
- [AI club](https://lp.jetbra...
Educational Codeforces Round 170 [Rated for Div. 2], Educational Codeforces Round 170 [рейтинговый для Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Neapolis University Pafos, The problems were invented and prepared by Adilbek [user:adedalic,2024-10-13]
Dalabaev, Ivan, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Задачи вместе со мной придумывали и готовили Адилбек [user:adedalic,2024-10-13]
Далабаев, Иван
Announcement of Educational Codeforces Round 170 (Rated for Div. 2)
45.
Educational Codeforces Round 86 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1342] [contest:1342] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-04-25] Glazov, Adilbek [user:adedalic,2020-04-25] Dalabaev, Vladimir [user:vovuh,2020-04-25] Petrov, Ivan [us...
Educational Codeforces Round 86 [Rated for Div. 2], Educational Codeforces Round 86 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, %;"/> _Hi Codeforces!_ _You really went for it in the last Educational Round!
We had an all-time, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 86 (Rated for Div. 2)
46.
Educational Codeforces Round 84 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1327] [contest:1327] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-03-22] Glazov, Adilbek [user:adedalic,2020-03-22] Dalabaev, Vladimir [user:vovuh,2020-03-22] Petrov, Ivan [user:Bl...
Educational Codeforces Round 84 [Rated for Div. 2], Educational Codeforces Round 84 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1327] [contest:1327] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 84 (Rated for Div. 2)
47.
Codeforces Round 1054 (Div. 3) Hello, Codeforces!
I am very excited to invite you to our contest [Codeforces Round 1054 (Div. 3)](https://codeforces.me/contest/2149), which starts on <a class="contest-time" contestid="2149" href="https://www.timeanddate.com/worldclock/fixedtime.html?day=25&month=9&year=2025&hour=17&min=35&sec=0&p1=166">. You will be given 7 problems and 2 hours and 15 minutes to solve them.
The problems were authored by me and [user:__rose,2025-09-22] and [user:soullless,2025-09-23] to solve and alter them.
The round will be hosted by the rules of educational rounds (extended **ICPC**). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a **12-hour phase** of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution — rank will be determined by number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of 10 m...
Codeforces Round 1054 (Div. 3), The round will be hosted by the rules of educational rounds (extended
**ICPC**). Thus, all
Announcement of Codeforces Round 1054 (Div. 3)
48.
Educational Codeforces Round 151 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1845] [contest:1845] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="https://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-06-28] Dalabaev, Ivan [user:BledDest,2023-06-28] Androsov, Maksim [user:Neon,2023-06-28] Mesch...
Educational Codeforces Round 151 [Rated for Div. 2], Educational Codeforces Round 151 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1845] [contest:1845] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 151 (Rated for Div. 2)
49.
Codeforces Round 1114 (Div. 3) Hello, Codeforces!
------------------
I am very excited to invite you to participate in [contest:2254], which will take place on [contest_time:2254]. You will be given $2$ hours and $15$ minutes to solve $7$ problems, where one problem will be split into subtasks. All problems were authored and prepared by me.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of **open hacks**. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of **10 minutes** for each wrong submission, following the rules of educational rounds.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure fo...
Codeforces Round 1114 (Div. 3), The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1114 (Div. 3)
50.
Codeforces Round #590 (Div. 3) **UPD**: Special thanks to Mikhail [user:PikMike,2019-10-01] Piklyaev for help with translation and problems discussing, Maksim [user:Ne0n25,2019-10-01] Mescheryakov for problems discussing, Artem [user:Rox,2019-10-01] Plotkin, Daria [user:ZeroAmbition,2019-10-01] Stepanova and Tommy [user:STommydx,2019-10-01] Li for testing the round!
**UPD2**: [Editorial](https://codeforces.me/blog/entry/70233) is published!
<almost-copy-pasted-part>
Hello!
[contest:1234] will start at [contest_time:1234]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried ...
Codeforces Round #590 (Div. 3), ,2019-10-01] Li for testing the round! **UPD2**:
[Editorial](https://codeforces.me/blog/entry
Announcement of Codeforces Round 590 (Div. 3)
51.
Educational Codeforces Round 142 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1792] [contest:1792] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-01-23] Dalabaev, Vladimir [user:vovuh,2023-01-23] Petrov, Ivan [user:BledDest,2023-01-23] Androsov, Ma...
Educational Codeforces Round 142 [Rated for Div. 2], Educational Codeforces Round 142 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1792] [contest:1792] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 142 (Rated for Div. 2)
52.
Codeforces Round #690 (Div. 3) Hello, Codeforces!
\<almost-copy-pasted-part\>
Hello! [Codeforces Round #690 (Div. 3)](https://codeforces.me/contest/1462) will start at [contest_time:1462]. You will be offered 6 problems (one of them is split into two subtasks) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember](https://codeforces.me/bl...
Codeforces Round #690 (Div. 3), educational rounds (extended ACM-ICPC). Thus, during the round, solutions will
be judged on
Announcement of Codeforces Round 690 (Div. 3)
53.
EPIC Institute of Technology Round Summer 2025 (Codeforces Round 1036, Div. 1 + Div. 2) # Hello Codeforces Once Again
<img alt="" src="https://codeforces.me/predownloaded/4e/71/4e713a365fc86888c808b3b56d6fecfb529973e6.png" style="float:right; height: 154px; padding-left: 35px; padding-right: 73px; padding-top: 41px; padding-bottom: 33px;"/>
After months of hard work, [user:cry,2025-07-01], [user:Lilypad,2025-07-01] and I are extremely proud to welcome you to participate in [contest:2124] at [contest_time:2124]. This round is combined for Division 1 and Division 2, and it will be rated for everyone.
You will be given $3$ hours to solve $9$ problems. One problem will be split into two subtasks.
We would like to thank the following people for making the contest possible:
- [user:satyam343,2025-07-01] for outstanding coordination, working tirelessly with us to improve problem quality and donating his own problems to us. I cannot thank him enough.
- [user:Error_Yuan,2025-07-01] for proposing some ideas that weren't used in the end.
- [user:Benq,2025-07-01...
EPIC Institute of Technology Round Summer 2025 (Codeforces Round 1036, Div. 1 +
Div. 2), in [contest:2124] at [contest_time:2124]. This round is combined for Division
1 and Division 2, and
54.
Educational Codeforces Round 180 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/). They offer a BSc in Computer Science and AI with [JetBrains Scholarships] (https://lp.jetbrains.com/academy/csai-program/). Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Curious? Check out the [CSAI curriculum] (https://drive.google.com/file/d/19I776O8NG07ie2Q14wwBspuh3De4kbHc/view). Limited scholarships available — don't miss your chance to study in Europe for free!
On [contest_time:2112] [contest:2112] will start.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a ful...
Educational Codeforces Round 180 [Rated for Div. 2], Educational Codeforces Round 180 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, ! The series of Educational Rounds continues thanks to the support of the
[Neapolis University Pafos, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 180 (Rated for Div. 2)
55.
Educational Codeforces Round 115 [Rated for Div.2] Hello Codeforces!
On [contest_time:1598] [contest:1598] will start. **Note that the start time is unusual**.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Alex [user:fcspartakm,2021-10-09] Frolov, Mikhail [user:awoo,2021-10-09] Piklyaev, Max [...
Educational Codeforces Round 115 [Rated for Div.2], Educational Codeforces Round 115 [рейтинговый для Div. 2], is unusual**. Series of Educational Rounds continue being held as
[Harbour.Space University, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, посылки, являющейся полным решением, равен 10 минутам. После окончания раунда
будет период времени, The problems were invented and prepared by Alex [user:fcspartakm,2021-10-09]
Frolov, Mikhail, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, _We are thrilled to congratulate our faculty member Nikolay [user:KAN,2021-10
-09] Kalinin on his, _We would also like to congratulate our future student Egor [user:kefaa2,2021-10
-09] Dubovik, who, _Мы поздравляем одного из наших преподавателей Николая [user:KAN,2021-10-09]
Калинина с его первым, _Также поздравляем нашего будущего студента Егора [user:kefaa2,2021-10-09]
Дубовика, завоевавшего, Задачи вместе со мной придумывали и готовили Александр [user:fcspartakm,2021-10
-09] Фролов, Михаил
Announcement of Educational Codeforces Round 115 (Rated for Div. 2)
56.
Educational Codeforces Round 143 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1795] [contest:1795] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-02-15] Dalabaev, Vladimir [user:vovuh,2023-02-15] Petrov, Ivan [user:BledDest,2023-02-15] Androsov, Ma...
Educational Codeforces Round 143 [Rated for Div. 2], Educational Codeforces Round 143 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 143 (Rated for Div. 2)
57.
Codeforces Round #653 (Div. 3) <almost-copy-pasted-part>
Hello!
[contest:1374] will start at [contest_time:1374]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the ...
Codeforces Round #653 (Div. 3), educational rounds (extended ACM-ICPC). Thus, during the round, solutions will
be judged on
Announcement of Codeforces Round 653 (Div. 3)
58.
Educational Codeforces Round 190 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Computer Science and Artificial Intelligence (CSAI)] (https://lp.jetbrains.com/academy/csai-program/) program at [Neapolis University Pafos](https://www.nup.ac.cy/), with scholarships provided by JetBrains.
[contest:2230] will start on [contest_time:2230].
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
**The problems in this round will partially intersect with Saratov SU internal contest (schedul...
Educational Codeforces Round 190 [Rated for Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Computer Science and, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 190 (Rated for Div. 2)
59.
Educational Codeforces Round 98 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1452] [contest:1452] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-11-18] Glazov, Adilbek [user:adedalic,2020-11-18] Dalabaev, Vladimir [user:vovuh,2020-11-18] Petrov, Ivan [us...
Educational Codeforces Round 98 [Rated for Div. 2], Educational Codeforces Round 98 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1452] [contest:1452] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 98 (Rated for Div. 2)
60.
Educational Codeforces Round 111 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1550] [contest:1550] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2021-07-13] Dalabaev, Vladimir [user:vovuh,2021-07-13] Petrov, Ivan [user:BledDest,2021-07-13] Androsov, Mak...
Educational Codeforces Round 111 [Rated for Div. 2], Educational Codeforces Round 111 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1550] [contest:1550] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 111 (Rated for Div. 2)
61.
Educational Codeforces Round 155 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1879] [contest:1879] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="https://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-09-23] Dalabaev, Ivan [user:BledDest,2023-09-23] Androsov, Maksim [user:Neon,2023-09-23] Mesch...
Educational Codeforces Round 155 [Rated for Div. 2], Educational Codeforces Round 155 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1879] [contest:1879] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 155 (Rated for Div. 2)
62.
Codeforces Round #661 (Div. 3) Hello!
[contest:1399] will start at [contest_time:1399]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the official standings table. As it is ...
Codeforces Round #661 (Div. 3), the round unofficially. The round will be hosted by rules of educational
rounds (extended ACM
Announcement of Codeforces Round 661 (Div. 3)
63.
Educational Codeforces Round 145 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1809] [contest:1809] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-03-19] Dalabaev, Ivan [user:BledDest,2023-03-19] Androsov, Maksim [user:Neon,2023-03-19] Mescheryakov ...
Educational Codeforces Round 145 [Rated for Div. 2], Educational Codeforces Round 145 [рейтинговый для Div. 2], inviting students ages 10 to 18 interested in improving their skills or
seeking intensive, high, полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, программированию. Мы приглашаем учащихся в возрасте от 10 до 18 лет,
заинтересованных в улучшении своих, Hello Codeforces! On [contest_time:1809] [contest:1809] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 145 (Rated for Div. 2)
64.
Educational Codeforces Round 114 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1574] [contest:1574] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2021-09-19] Dalabaev, Vladimir [user:vovuh,2021-09-19] Petrov, Ivan [user:BledDest,2021-09-19] Androsov, Mak...
Educational Codeforces Round 114 [Rated for Div. 2], Educational Codeforces Round 114 [рейтинговый для Div. 2], полным решением, равен 10 минутам. После окончания раунда будет период времени
длительностью в 12, Hello Codeforces! On [contest_time:1574] [contest:1574] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 114 (Rated for Div. 2)
65.
Educational Codeforces Round 102 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1473] [contest:1473] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-01-13] Glazov, Adilbek [user:adedalic,2021-01-13] Dalabaev, Vladimir [user:vovuh,2021-01-13] Petrov, Ivan [us...
Educational Codeforces Round 102 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 102 (Rated for Div. 2)
66.
Educational Codeforces Round 194 [rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 150px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/).
[contest:2260] will start on [contest_time:2260].
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them. I hope everyone participating finds interesting problems for them to solve.
I would like to express my gratitude to Mike [user:MikeMirzayanov,2026-09-06] Mirzayanov for creating Cod...
Educational Codeforces Round 194 [rated for Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Neapolis University Pafos, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 194 (Rated for Div. 2)
67.
Educational Codeforces Round 108 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1519] [contest:1519] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-04-28] Glazov, Adilbek [user:adedalic,2021-04-28] Dalabaev, Vladimir [user:vovuh,2021-04-28] Petrov, Ivan [us...
Educational Codeforces Round 108 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 108 (Rated for Div. 2)
68.
Educational Codeforces Round 71 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1207] [contest:1207] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-08-06] Glazov, Adilbek [user:adedalic,2019-08-06] Dalabaev, Vladimir [user:Vovuh,2019-08-06] Petrov, Ivan [user:Bl...
Educational Codeforces Round 71 [Rated for Div. 2], Hello Codeforces! On [contest_time:1207] [contest:1207] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 71 (Rated for Div. 2)
69.
Educational Codeforces Round 67 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1187] [contest:1187] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-06-04] Glazov, Adilbek [user:adedalic,2019-06-04] Dalabaev, Vladimir [user:Vovuh,2019-06-04] Petrov, Ivan [user:Bl...
Educational Codeforces Round 67 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 67 (Rated for Div. 2)
70.
Codeforces Round #686 (Div. 3) Hello!
[contest:1454] will start at [contest_time:1454]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the official standings table. As it is ...
Codeforces Round #686 (Div. 3), the round unofficially. The round will be hosted by rules of educational
rounds (extended ACM
Announcement of Codeforces Round 686 (Div. 3)
71.
Educational Codeforces Round 94 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1400] [contest:1400] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-08-24] Glazov, Adilbek [user:adedalic,2020-08-24] Dalabaev, Vladimir [user:vovuh,2020-08-24] Petrov, Ivan [us...
Educational Codeforces Round 94 [Rated for Div. 2], Hello Codeforces! On [contest_time:1400] [contest:1400] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 94 (Rated for Div. 2)
72.
Educational Codeforces Round 131 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1701] [contest:1701] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-07-07] Dalabaev, Vladimir [user:vovuh,2022-07-07] Petrov, Ivan [user:BledDest,2022-07-07] Androsov, Mak...
Educational Codeforces Round 131 [Rated for Div. 2], Educational Codeforces Round 131 [рейтинговый для Div. 2], world with the 10 days intensive Summer Camp organized by Harbour.Space and
Leagues of Code._, программирования с 10-дневным интенсивным летним лагерем, который организован
Harbour.Space и Leagues of, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, educational round hosted by Harbour.Space and Codeforces._ _Quite exciting,
isn’t it? Now it's time
Announcement of Educational Codeforces Round 131 (Rated for Div. 2)
73.
After a Round FAQ Every time a (rated) round ends, I always see the same questions from people who are new to Codeforces. So, here I made an FAQ that answers to these repeated questions. Please do provide the link to this blog when you want to answer to them.
#### Why is my rating still not updated yet?
Be patient. It takes a while (can be a few hours, or even more) to finalize things such as detecting cheats and confirming test results, or there can be other issues that need investigation. It won't be unrated unless they announced that it will be unrated.
#### My solution was hacked after contest, but why didn't my rank / rating change?
It is called _uphacking_, and it does NOT affect the standings nor rating changes. The score you gained from uphacked solution will remain. The hack tests will be added to the tests for practice submissions later, but there won't be any rejudges on already accepted solutions.
#### I got a system message that says that my submission coincides with other soluti...
After a Round FAQ, #### (Educational & Div. 3/4 rounds) It has been 10 hours after the contest,
why is my rating still
74.
Educational Codeforces Round 113 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1569] [contest:1569] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2021-09-07] Dalabaev, Vladimir [user:vovuh,2021-09-07] Petrov, Ivan [user:BledDest,2021-09-07] Androsov, Mak...
Educational Codeforces Round 113 [Rated for Div. 2], Hello Codeforces! On [contest_time:1569] [contest:1569] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 113 (Rated for Div. 2)
75.
Codeforces Round 1131 (Div. 3) #**Trick or participate, Codeforces?**
We are glad to invite you to our <a class="rated-user user-orange">Halloween</a> round, [contest:2278], which will start on [contest_time:2278].
The problems were authored by [user:wuhudsm,2026-10-27], and prepared by [user:wuhudsm,2026-10-27] and [user:wakanda-forever,2026-10-27]
You will be given **7 problems** and **135 minutes** to solve.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**. After open hacks all accepted solutions will be rejudged on successful hacks.
Note that the **penalty** for each wrong submission in this round is **10 minutes**. Also, **note the [rule restricting AI use](https://codeforces.me/blog/entry/133941)!!!** If you are caught using AI in an unorthodox manner, bad things will happen to you. We will be watching you all...
[Remember](https://...
Codeforces Round 1131 (Div. 3), . The round will be hosted by rules of educational rounds (extended ICPC).
Thus, solutions will be
Announcement of Codeforces Round 1131 (Div. 3)
76.
Codeforces Round #903 (Div. 3) Hello! [contest:1881] will start at [contest_time:1881]. You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a _trusted participant of the third...
Codeforces Round #903 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus
Announcement of Codeforces Round 903 (Div. 3)
77.
Codeforces Round #760 (Div. 3) Hello, Codeforces!
On [contest_time:1618] the [contest:1618] will start. This is a usual round for the participants from the third division. The round will contain 8 problems, which are mostly suited for participants with rating below 1600 (or we hope so). Although, as usual, participants with rating of 1600 and greater can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks (we hope that our tests are strong enough, so there won't be too many solutions hacked during this phase).
You will have to solve **8 problems** in **2 hours and 15 minutes**. The penalty for a wrong submission is equal to **10 minutes**.
[We remind you](https://codeforces.me/blog/entry/59228) that only _the trusted participants of the third division_ will be included in the official standings table. As it is w...
Codeforces Round #760 (Div. 3), rules of educational rounds (extended ACM-ICPC). Thus, during the round,
solutions will be judged on
Announcement of Codeforces Round 760 (Div. 3)
78.
Educational Codeforces Round 150 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1841] [contest:1841] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-06-11] Dalabaev, Ivan [user:BledDest,2023-06-11] Androsov, Maksim [user:Neon,2023-06-11] Mesche...
Educational Codeforces Round 150 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 150 (Rated for Div. 2)
79.
Codeforces Round #642 (Div. 3) <almost-copy-pasted-part>
Hello!
[contest:1353] will start at [contest_time:1353]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the ...
Codeforces Round #642 (Div. 3), educational rounds (extended ACM-ICPC). Thus, during the round, solutions will
be judged on
Announcement of Codeforces Round 642 (Div. 3)
80.
Educational Codeforces Round 147 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1821] [contest:1821] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-04-19] Dalabaev, Ivan [user:BledDest,2023-04-19] Androsov, Maksim [user:Neon,2023-04-19] Mesche...
Educational Codeforces Round 147 [Rated for Div. 2], Hello Codeforces! On [contest_time:1821] [contest:1821] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 147 (Rated for Div. 2)
81.
Educational Codeforces Round 132 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1709] [contest:1709] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-07-20] Dalabaev, Vladimir [user:vovuh,2022-07-20] Petrov, Ivan [user:BledDest,2022-07-20] Androsov, Mak...
Educational Codeforces Round 132 [Rated for Div. 2], Hello Codeforces! On [contest_time:1709] [contest:1709] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 132 (Rated for Div. 2)
82.
Educational Codeforces Round 195 [rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 150px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/).
[contest:2276] will start on [contest_time:2276].
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them. I hope everyone participating finds interesting problems for them to solve.
**The round is based on the problems from The ICPC Southern and Volga Russia Regional Contest. If you par...
Educational Codeforces Round 195 [rated for Div. 2], Educational Codeforces Round 195 [рейтинговый для Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Neapolis University Pafos, I would like to express my gratitude to Mike [user:MikeMirzayanov,2026-10-12]
Mirzayanov for, The problems were prepared by [user:fcspartakm,2026-10-12], [user:Roms,2026-10
-12] and me., This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Задачи вместе со мной готовили [user:fcspartakm,2026-10-12] и [user:Roms,2026-10
-12]., Я бы хотел поблагодарить Михаила [user:MikeMirzayanov,2026-10-12] Мирзаянова за
создание платформ
Announcement of Educational Codeforces Round 195 (Rated for Div. 2)
83.
Educational Codeforces Round 70 Editorial [problem:1202A]
Idea: [user:adedalic,2019-08-08]
<spoiler summary="Tutorial">
[tutorial:1202A]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
fun main(args: Array<String>) {
val T = readLine()!!.toInt()
for (tc in 1..T) {
val x = readLine()!!.reversed()
val y = readLine()!!.reversed()
val posY = y.indexOf('1')
val posX = x.indexOf('1', posY)
println(posX - posY)
}
}
~~~~~
</spoiler>
[problem:1202B]
Idea: [user:adedalic,2019-08-08]
<spoiler summary="Tutorial">
[tutorial:1202B]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
const val INF = 1e9.toInt()
fun main(args: Array<String>) {
val s = readLine()!!.map { it - '0' }
val cf = Array(10) {Array(10) {0}}
for (i in 1 until s.size)
cf[s[i - 1]][s[i]]++
for (x in 0..9) {
for (y in 0..9) {
val ds = Array(10) {Array(10) {INF + 7}}
for (v in 0..9) {
...
Educational Codeforces Round 70 Editorial, Разбор Educational Codeforces Round 70, for (x in 0..9) { for (y in 0..9) { val ds = Array(10) {Array(10) {INF + 7}}, fun main(args: Array) { val s = readLine()!!.map { it - '0' } val cf = Array(10, val to = (v + cx * x + cy * y) % 10 ds[v][to] = minOf(ds[v][to], cx + cy) } } }
84.
Codeforces Round #667 (Div. 3) Hello!
[contest:1409] will start at [contest_time:1409]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the official standings table. As it is ...
Codeforces Round #667 (Div. 3), the round unofficially. The round will be hosted by rules of educational
rounds (extended ACM
Announcement of Codeforces Round 667 (Div. 3)
85.
Educational Codeforces Round 45 [Rated for Div. 2] Hello Codeforces!
On [contest_time:990] Educational Codeforces Round 45 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ACM ICPC rules. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2018-06-09] Dalabaev, Roman [user:Ajosteen,2018-06-09] Glazov, Ivan [user:BledDest,2018-06-09] Androsov, Mike [user:MikeMirzayanov,2018-06-09] Mirzayanov and me.
Good luck to all particip...
Educational Codeforces Round 45 [Rated for Div. 2], Educational Codeforces Round 45 [рейтинговый для Div. 2], Hello Codeforces! On [contest_time:990] Educational Codeforces Round 45 will
start. Series, Привет, Codeforces! В [contest_time:990] состоится Educational Codeforces Round
45
86.
Codeforces Round #634 (Div. 3) <almost-copy-pasted-part>
Hello!
[contest:1335] will start at [contest_time:1335]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the ...
Codeforces Round #634 (Div. 3), educational rounds (extended ACM-ICPC). Thus, during the round, solutions will
be judged on
Announcement of Codeforces Round 634 (Div. 3)
87.
Codeforces Round #925 (Div. 3) Hello! [contest:1931] will start at [contest_time:1931]. You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a _trusted participant of the third...
Codeforces Round #925 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus
Announcement of Codeforces Round 925 (Div. 3)
88.
Codeforces Round #693 (Div. 3) Happy New Year, Codeforces!
UPD: _**We have received such different opinions about the order of problems, that we cannot be completely sure about it. We recommend you to read all the problems and do not strongly hope that the difficulty for you necessarily coincides with the order in the round.**_
\<almost-copy-pasted-part\>
Hello! [Codeforces Round #693 (Div. 3)](https://codeforces.me/contest/1472) will start at [contest_time:1472]. You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. We tried to make strong tests — just like you will be upset if many solutions fail after t...
Codeforces Round #693 (Div. 3), unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus, during theround
Announcement of Codeforces Round 693 (Div. 3)
89.
Codeforces Round #595 (Div. 3) **UPD**: Thanks to Daria [user:ZeroAmbition,2019-10-22] Stepanova, Mikhail [user:PikMike,2019-10-22] Piklyaev and Artem [user:Rox,2019-10-22] Plotkin for help with round preparation!
**UPD2**: [Editorial](https://codeforces.me/blog/entry/70779) is published!
<almost-copy-pasted-part>
Hello!
[contest:1249] will start at [contest_time:1249]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and ...
Codeforces Round #595 (Div. 3), ] Piklyaev and Artem [user:Rox,2019-10-22] Plotkin for help with round
preparation! **UPD2
Announcement of Codeforces Round 595 (Div. 3)
90.
Educational Codeforces Round 109 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1525] [contest:1525] will start. **Please, note the unusual start time.**
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-05-15] Glazov, Adilbek [user:adedalic,2021-05-15] Dalabaev, Vladimir...
Educational Codeforces Round 109 [Rated for Div. 2], start time.** Series of Educational Rounds continue being held as
[Harbour.Space University](https, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 109 (Rated for Div. 2)
91.
Educational Codeforces Round 91 Editorial [problem:1380A]
Idea: [user:BledDest,2020-07-12]
<spoiler summary="Tutorial">
[tutorial:1380A]
</spoiler>
<spoiler summary="Solution (Ne0n25)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
const int N = 1000;
int n;
int a[N];
void solve() {
cin >> n;
for (int i = 0; i < n; ++i)
cin >> a[i];
for (int i = 1; i < n - 1; ++i) {
if (a[i] > a[i - 1] && a[i] > a[i + 1]) {
cout << "YES" << endl;
cout << i << ' ' << i + 1 << ' ' << i + 2 << endl;
return;
}
}
cout << "NO" << endl;
}
int main() {
int T;
cin >> T;
while (T--)
solve();
}
~~~~~
</spoiler>
[problem:1380B]
Idea: [user:adedalic,2020-07-12]
<spoiler summary="Tutorial">
[tutorial:1380B]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
fun main() {
val winBy = mapOf('R' to 'P', 'S' to 'R', 'P' to 'S')
repeat(readLine()!!.toInt()) {
val s = readLine()!!
val maxCnt = s.groupingBy { it }.eachCount().maxBy ...
Educational Codeforces Round 91 Editorial, Разбор Educational Codeforces Round 91, ] = add(c.val[na + nb], mul(mul(a.val[0], b.val[0]), 19 - (l * 10 + r)));
c.val[1 + na] = add(c.val, int n, m; string s; int dp[N][10]; int idp[N][10]; set > lr; int res = 1;
92.
Educational Codeforces Round 119 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1620] [contest:1620] will start. **Please, note the unusual start time.**
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2021-12-17] Dalabaev, Vladimir [user:vovuh,2021-12-17] Petrov, Ivan...
Educational Codeforces Round 119 [Rated for Div. 2], start time.** Series of Educational Rounds continue being held as
[Harbour.Space University](https, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 119 (Rated for Div. 2)
93.
Codeforces Round 1059 (Div. 3) ### Hello, Codeforces!
I am very excited to invite you to our contest [Codeforces Round 1059 (Div. 3)](https://codeforces.me/contest/2162), which starts on [contest_time:2162]. You will be given $2$ hours and $15$ minutes to solve $8$ problems.
The problems were authored and prepared by [user:wakanda-forever,2025-10-10], [user:wuhudsm,2025-10-10], [user:tridipta2806,2025-10-10] and [user:tamzid1,2025-10-10].
Note that at least one of the problems will be interactive. So if you are unfamiliar with them, please read the [guide for interactive problems](https://codeforces.me/blog/entry/45307) before the contest.
The round will be hosted by the rules of educational rounds (extended <b>ICPC</b>). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a <b>12-hour phase</b> of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution —...
Codeforces Round 1059 (Div. 3), /entry/45307) before the contest. The round will be hosted by the rules of
educational rounds, The round will be hosted by the rules of educational rounds (extended ICPC).
Thus, all
Announcement of Codeforces Round 1059 (Div. 3)
94.
Educational Codeforces Round 112 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1555] [contest:1555] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2021-07-29] Dalabaev, Vladimir [user:vovuh,2021-07-29] Petrov, Ivan [user:BledDest,2021-07-29] Androsov, Mak...
Educational Codeforces Round 112 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 112 (Rated for Div. 2)
95.
Educational Codeforces Round 48 [Rated for Div. 2] On [contest_time:1016] Educational Codeforces Round 48 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ACM ICPC rules. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Ivan [user:BledDest,2018-08-02] Androsov, Roman [user:Ajosteen,2018-08-02] Glazov, Adilbek [user:adedalic,2018-08-02] Dalabaev, Vladimir [user:Vovuh,2018-08-02] Petrov and me.
Good luck to all participants!
Congratulations to th...
Educational Codeforces Round 48 [Rated for Div. 2], On [contest_time:1016] Educational Codeforces Round 48 will start. Series of
Educational Rounds
96.
Educational Codeforces Round 133 Editorial [problem:1716A]
Idea: [user:vovuh,2022-08-05]
<spoiler summary="Tutorial">
[tutorial:1716A]
</spoiler>
<spoiler summary="Solution (vovuh)">
~~~~~
for _ in range(int(input())):
n = int(input())
print(1 + (n == 1) if n <= 3 else (n + 2) // 3)
~~~~~
</spoiler>
[problem:1716B]
Idea: [user:BledDest,2022-08-05]
<spoiler summary="Tutorial">
[tutorial:1716B]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
n = int(input())
p = [i + 1 for i in range(n)]
print(n)
for i in range(n):
print(*p)
if i < n - 1:
p[i], p[i + 1] = p[i + 1], p[i]
~~~~~
</spoiler>
[problem:1716C]
Idea: [user:BledDest,2022-08-05]
<spoiler summary="Tutorial">
[tutorial:1716C]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
INF = 2 * 10**9
for _ in range(int(input())):
m = int(input())
a = [[int(x) for x in input().split()] for i in range(2)]
su = [[-INF for j in range(m + 1)] for i in range(2...
Educational Codeforces Round 133 Editorial, Разбор Educational Codeforces Round 133, ~~~~~ INF = 2 * 10**9
97.
I compiled a list of almost all useful blogs ever published on Codeforces [update: till 09.06.2021] <h3 style="color:red">If there are any blogs that I have missed, please tell in the comment section. Thank you.</h3>
# Mathematics Stuff
- [Number Theory in Competitive Programming [Tutorial]](https://codeforces.me/blog/entry/46620)
- [Number of points on Convex hull with lattice points](https://codeforces.me/blog/entry/62183)
- [FFT, big modulos, precision errors.](https://codeforces.me/blog/entry/48465)
- [Number of ways between two vertices](https://codeforces.me/blog/entry/19078)
- [Mathematics For Competitive Programming](https://codeforces.me/blog/entry/76938)
- [FFT and NTT](https://codeforces.me/blog/entry/19862)
- [Burnside Lemma](https://codeforces.me/blog/entry/51272)
- [Number of positive integral solutions of equation 1/x+1/y=1/n!](https://codeforces.me/blog/entry/76836)
- [On burnside (again)](https://codeforces.me/blog/entry/64860)
- [Simple but often unknown theorems/lemmas/formula? Do you know?](https://codeforces.me/blog/entry/55912)
- [Probabili...
/entry/15729) - [Educational Round 83 problem E (Array Shrinking): O(n log n)
solution](https
98.
Educational Codeforces Round 107 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1511] [contest:1511] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-04-11] Glazov, Adilbek [user:adedalic,2021-04-11] Dalabaev, Vladimir [user:vovuh,2021-04-11] Petrov, Ivan [us...
Educational Codeforces Round 107 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 107 (Rated for Div. 2)
99.
Educational Codeforces Round 42 (Rated for Div. 2) Hello Codeforces!
On [April 10, 14:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=10&month=4&year=2018&hour=17&min=35&sec=0&p1=166) Educational Codeforces Round 42 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for Div. 2**. It will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by me and Alex [user:fcspartakm,2018-04-09] Frolov.
We'd like to thank Nikolay [user:KAN,2018-04-09] Kalinin, Grigory [user:gritukan,2018-04-09] Reznikov,...
Educational Codeforces Round 42 (Rated for Div. 2), Educational Codeforces Round 42 (рейтинговый для Див. 2), &year=2018&hour=17&min=35&sec=0&p1=166) начнётся Educational Codeforces Round
42., ; and especially recognise division A’s winner: Team SDV — Vasily
[user:platypus179,2018-04-10, =2018&hour=17&min=35&sec=0&p1=166) Educational Codeforces Round 42 will start.
Announcement of Educational Codeforces Round 42 (Rated for Div. 2)
100.
Educational Codeforces Round 123 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1644] [contest:1644] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-02-21] Dalabaev, Vladimir [user:vovuh,2022-02-21] Petrov, Ivan [user:BledDest,2022-02-21] Androsov, Mak...
Educational Codeforces Round 123 [Rated for Div. 2], Hello Codeforces! On [contest_time:1644] [contest:1644] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 123 (Rated for Div. 2)
101.
Educational Codeforces Round 182 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/). They offer a BSc in Computer Science and AI with [JetBrains Scholarships] (https://lp.jetbrains.com/academy/csai-program/). Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Limited scholarships available — don't miss your chance to study in Europe for free!
On [contest_time:2144] [contest:2144] will start.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You w...
Educational Codeforces Round 182 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 182 (Rated for Div. 2)
102.
Educational Codeforces Round 187 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Computer Science and Artificial Intelligence (CSAI)] (https://lp.jetbrains.com/academy/csai-program/) program at [Neapolis University Pafos](https://www.nup.ac.cy/), with scholarships provided by JetBrains.
[contest:2203] will start on [contest_time:2203].
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6-7 problems** and **2 hours** to solve them.
The problems were invent...
Educational Codeforces Round 187 [Rated for Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Computer Science and, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 187 (Rated for Div. 2)
103.
Codeforces Round #677 (Div. 3) Hello!
[contest:1433] will start at [contest_time:1433]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the official standings table. As it is ...
Codeforces Round #677 (Div. 3), the round unofficially. The round will be hosted by rules of educational
rounds (extended ACM
Announcement of Codeforces Round 677 (Div. 3)
104.
Educational Codeforces Round 92 Editorial [problem:1389A]
Idea: [user:BledDest,2020-07-30]
<spoiler summary="Tutorial">
[tutorial:1389A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
l, r = map(int, input().split())
if l * 2 > r:
print(-1, -1)
else:
print(l, l * 2)
~~~~~
</spoiler>
[problem:1389B]
Idea: [user:Roms,2020-07-30]
<spoiler summary="Tutorial">
[tutorial:1389B]
</spoiler>
<spoiler summary="Solution 1 (pikmike)">
~~~~~
for _ in range(int(input())):
n, k, z = map(int, input().split())
a = [int(x) for x in input().split()]
ans = 0
s = 0
mx = 0
for t in range(z + 1):
pos = k - 2 * t
if pos < 0:
continue
mx = 0
s = 0
for i in range(pos + 1):
if i < n - 1:
mx = max(mx, a[i] + a[i + 1])
s += a[i]
ans = max(ans, s + mx * t)
print(ans)
~~~~~
</spoiler>
<spoiler summary="Solution 2 (pikmike)">
~~~~~
for _ in range(int(input())):
n, k, z = map(int, ...
Educational Codeforces Round 92 Editorial, Разбор Educational Codeforces Round 92, void solve() { string s; cin >> s; int ans = 0; forn(x, 10) forn(y, 10) ans =
max(ans
105.
Codeforces Round #826 (Div. 3) Hello! [contest:1741] will start at [contest_time:1741]. You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **6-8 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a _trusted participant of the thi...
Codeforces Round #826 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus
Announcement of Codeforces Round 826 (Div. 3)
106.
Codeforces Round #629 (Div. 3) <almost-copy-pasted-part>
Hello!
[contest:1328] will start at [contest_time:1328]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the ...
Codeforces Round #629 (Div. 3), educational rounds (extended ACM-ICPC). Thus, during the round, solutions will
be judged on
Announcement of Codeforces Round 629 (Div. 3)
107.
Educational Codeforces Round 134 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1721] [contest:1721] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-08-26] Dalabaev, Vladimir [user:vovuh,2022-08-26] Petrov, Ivan [user:BledDest,2022-08-26] Androsov, Mak...
Educational Codeforces Round 134 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 134 (Rated for Div. 2)
108.
Educational Codeforces Round 61 [Rated for Div. 2] 
Hello Codeforces!
On [contest_time:1132] [contest:1132] will start.
This round is organised in collaboration with Hello Muscat Programming Bootcamp and supported by Sberbank, General Partner of the boot camp and one of the largest banking leaders of Eastern Europe, providing thousands of jobs and innovation in the financial industry.
As the Hello Muscat Programming Bootcamp’s General Partner, Sberbank made it possible for students from some of the world’s top universities to attend the bootcamp, by sponsoring their participation. This includes students from Saint-Petersburg State University, Moscow Institute of Physics and Technology (MIPT), Penza State University, National Research Mordovia State University; MRSU, ITMO, Higher School of Economics / Moscow, Volgograd State Technical University, Lobachevsky State University of Nizhni Novgorod, Moscow Aviation Institute, Tyumen industrial University, University of Haifa, Northern (Arctic...
Educational Codeforces Round 61 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 61 (Rated for Div. 2)
109.
Complaining Again about Round 1056! **The blog doesn't interest you if you're not mentioned so skip reading to save your time!**
As you might've read in [user:Mr.Pie,2025-10-20]'s [blog post](https://codeforces.me/blog/entry/147075), some users have got rating change despite them being Master ranked and unrated in **Codeforces Round 1056 Div.2**, these are:<br>
[user:Rising-coder,2025-10-20] -me, [user:ivandasfs,2025-10-20], [user:saboten,2025-10-20], [user:konghaojie,2025-10-20], [user:GuilhermeCdM,2025-10-20], [user:yahia,2025-10-20], [user:CoderAbhi27,2025-10-20], [user:lyteabovenyte,2025-10-20]
### Why did this happen ?
It appears all of us have registered to the round when we were Candidate-Master. That's still a bug of course because I did the same many times before but this didn't happen.
### Why am I posting this blog ?
Well I tried contacting [user:MikeMirzayanov,2025-10-20], and the round coordinator [user:errorgorn,2025-10-20], and one of the authors [user:efishel,2025-10-20]. But they all read a...
Complaining Again about Round 1056!, Round 1056 Div.2**, these are:
[user:Rising-coder,2025-10-20] -me, [user:ivandasfs,2025-10-20
110.
Educational Codeforces Round 90 Editorial [problem:1373A]
Idea: [user:Roms,2020-06-26]
<spoiler summary="Tutorial">
[tutorial:1373A]
</spoiler>
<spoiler summary="Solution (pikmike)">
~~~~~
for tc in range(int(input())):
a, b, c = map(int, input().split())
print(1 if a < c else -1, end=" ")
print(b if c < a * b else -1)
~~~~~
</spoiler>
[problem:1373B]
Idea: [user:Roms,2020-06-26]
<spoiler summary="Tutorial">
[tutorial:1373B]
</spoiler>
<spoiler summary="Solution (Roms)">
~~~~~
for _ in range(int(input())):
s = input()
print('DA' if min(s.count('0'), s.count('1')) % 2 == 1 else 'NET')
~~~~~
</spoiler>
[problem:1373C]
Idea: [user:Roms,2020-06-26]
<spoiler summary="Tutorial">
[tutorial:1373C]
</spoiler>
<spoiler summary="Solution (Roms)">
~~~~~
for _ in range(int(input())):
s = input()
cur, mn, res = 0, 0, len(s)
for i in range(len(s)):
cur += 1 if s[i] == '+' else -1
if cur < mn:
mn = cur
res +=...
Educational Codeforces Round 90 Editorial, Разбор Educational Codeforces Round 90, + k < 10) cnt9 = 0; for(int j = 0; j <= cnt9; j++) { if(i + k >= 10 && j == 0, for tc in range(int(input())): n, k = map(int, input().split()) k += 1 bst = 10
**100 for d
111.
Codeforces Round #710 (Div. 3) Hello, Codeforces!
\<almost-copy-pasted-part\>
Hello! [Codeforces Round #710 (Div. 3)](https://codeforces.me/contest/1506) will start at [contest_time:1506]. You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 7 problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted partici...
Codeforces Round #710 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus
Announcement of Codeforces Round 710 (Div. 3)
112.
Sport programming and incorrect accepted solutions I didn't help but notice that almost each contest there's at least some solutions that are clearly incorrect but get accepted nevertheless.
For example, discussions for last 3 numbered CF rounds:
+ https://codeforces.me/blog/entry/62750?#comment-467811
+ https://codeforces.me/blog/entry/62692
+ https://codeforces.me/blog/entry/62594?#comment-465649
Sometimes problemsetters/testers could have done better job, sometimes it's seems close to impossible to fail specific solutions in advance without actually coming up with this solution.
So, here is an idea which I both thought of myself and also heard from several other people:
What if after the contest and system testing phase there was open hacking phase, which doesn't give any points for hackers but helps to find solutions that should not be accepted.
It seems that it should be easily implementable, considering it already works somewhat like this in Educational rounds, but [user:MikeMirzayanov,2018-10-28] may comment o...
Educational rounds, but [user:MikeMirzayanov,2018-10-28] may comment on that.
113.
Educational Codeforces Round 120 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1622] [contest:1622] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2021-12-26] Dalabaev, Vladimir [user:vovuh,2021-12-26] Petrov, Ivan [user:BledDest,2021-12-26] Androsov, Mak...
Educational Codeforces Round 120 [Rated for Div. 2], Hello Codeforces! On [contest_time:1622] [contest:1622] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 120 (Rated for Div. 2)
114.
Educational Codeforces Round 104 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1487] [contest:1487] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2021-02-14] Glazov, Adilbek [user:adedalic,2021-02-14] Dalabaev, Vladimir [user:vovuh,2021-02-14] Petrov, Ivan [us...
Educational Codeforces Round 104 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 104 (Rated for Div. 2)
115.
Codeforces Round 1009 (Div. 3) Oh hello there. This is [user:chromate00,2025-03-09], just casually on the announcement of [contest:2074]. And now, you see a drawing.
<h2><b><center>$\square$ — $\triangle$ — $\triangle$ — ◯ — $\triangle$ — $\square$ — $\triangle$</center></b></h2>
And then, you think. You see a square, a triangle, and a circle. Also, a Korean problemsetter. You immediately imagine the certain survival game that popped up in your memory. And you may be right. Or you might be wrong. Whatever, what I can ensure you is that you will be absolutely stunned to see the problems. Or astonished. You might not believe what you see. This round might change *everything*.
Anyways, the preface was a bit too long. Starting from [contest_time:2074], you will be given **$\mathbf{7}$ problems** to be solved in **$\mathbf{2.5}$ hours**. There is **at least one** interactive problem, so I strongly urge you to read [the guide](https://codeforces.me/blog/entry/45307) if you a...
Codeforces Round 1009 (Div. 3), The round will be hosted by rules of educational rounds (extended ICPC). Thus,
all solutions will
Announcement of Codeforces Round 1009 (Div. 3)
116.
Educational Codeforces Round 128 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1680] [contest:1680] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-05-12] Dalabaev, Vladimir [user:vovuh,2022-05-12] Petrov, Ivan [user:BledDest,2022-05-12] Androsov, Mak...
Educational Codeforces Round 128 [Rated for Div. 2], Hello Codeforces! On [contest_time:1680] [contest:1680] will start. Series of
Educational, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 128 (Rated for Div. 2)
117.
Educational Codeforces Round 68 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1194] [contest:1194] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-07-13] Glazov, Adilbek [user:adedalic,2019-07-13] Dalabaev, Vladimir [user:Vovuh,2019-07-13] Petrov, Ivan [user:Bl...
Educational Codeforces Round 68 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 68 (Rated for Div. 2)
118.
Educational Codeforces Round 186 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Computer Science and Artificial Intelligence (CSAI)] (https://lp.jetbrains.com/academy/csai-program/) program at [Neapolis University Pafos](https://www.nup.ac.cy/), with scholarships provided by JetBrains.
[contest:2182] will start on [contest_time:2182].
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6-7 problems** and **2 hours** to solve them.
The problems were invent...
Educational Codeforces Round 186 [Rated for Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Computer Science and, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 186 (Rated for Div. 2)
119.
Educational Codeforces Round 5 Hi, Codeforces!
Happy New Year! Holidays and 2015 year have passed and year 2016 is ahead. I wish you good luck in programming competitions and achieving all of your goals this year.
<img src="http://www.keviniriarte.com/wp-content/uploads/2014/04/new_season.jpg" style="max-width:100%; max-height:100%"/>
Educational Codeforces Round 5 will take place on [11 January 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+5&iso=20160111T1500) for the first and second divisions. You can read about educational rounds [here](http://codeforces.me/blog/entry/21496) and [here](http://codeforces.me/blog/entry/21565).
\<A year has passed, but paragraph remains unchanged.\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally...
Educational Codeforces Round 5, As usual the round was prepared by me, Edvard Davtyan. Thanks a lot to
[user:MikeMirzayanov,2016-01
Announcement of Educational Codeforces Round 5
120.
Educational Codeforces Round 137 Editorial [problem:1743A]
Idea: [user:fcspartakm,2022-10-18]
<spoiler summary="Tutorial">
[tutorial:1743A]
</spoiler>
<spoiler summary="Solution 1 (awoo)">
~~~~~
for _ in range(int(input())):
n = int(input())
a = set(map(int, input().split()))
ans = 0
for i in range(10000):
num = str(i)
num = (4 - len(num)) * '0' + num
used = set(num)
if len(used) != 2:
continue
d1 = int(used.pop())
d2 = int(used.pop())
if (not d1 in a) and (not d2 in a) and num.count(num[0]) == 2:
ans += 1
print(ans)
~~~~~
</spoiler>
<spoiler summary="Solution 2 (fcspartakm)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int n;
inline void read() {
cin >> n;
int x;
for (int i = 0; i < n; ++i)
cin >> x;
}
inline int fac(int n) {
int res = 1;
for (int i = 2; i <= n; i++) {
res *= i;
}
return res;
}
inline int c(int n, int k) {
return fac(n) / fac(k) / fac(n - k);
}
inline void sol...
Educational Codeforces Round 137 Editorial, Разбор Educational Codeforces Round 137, Idea: [user:BledDest,2022-10-18], Idea: [user:fcspartakm,2022-10-18], inline void solve() { cout << c(10 - n, 2) * c(4, 2) << endl; }, Идея: [user:BledDest,2022-10-18], Идея: [user:fcspartakm,2022-10-18]
121.
Educational Codeforces Round 75 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1251] [contest:1251] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-10-23] Glazov, Adilbek [user:adedalic,2019-10-23] Dalabaev, Vladimir [user:Vovuh,2019-10-23] Petrov, Ivan [user:Bl...
Educational Codeforces Round 75 [Rated for Div. 2], Hello Codeforces! On [contest_time:1251] [contest:1251] will start. Series of
Educational
Announcement of Educational Codeforces Round 75 (Rated for Div. 2)
122.
Educational Codeforces Round 171 Editorial [problem:2026A]
Idea: [user:adedalic,2024-10-29]
<spoiler summary="Tutorial">
[tutorial:2026A]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
int main() {
int t; cin >> t;
while (t--) {
int X, Y, K;
cin >> X >> Y >> K;
int M = min(X, Y);
cout << "0 0 " << M << " " << M << endl;
cout << "0 " << M << " " << M << " 0" << endl;
}
}
~~~~~
</spoiler>
[problem:2026B]
Idea: [user:BledDest,2024-10-29]
<spoiler summary="Tutorial">
[tutorial:2026B]
</spoiler>
<spoiler summary="Solution (Neon)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
int t;
cin >> t;
while (t--) {
int n;
cin >> n;
vector<long long> a(n);
for (auto& x : a) cin >> x;
long long ans = 1e18;
auto upd = [&](vector<long long> a) {
sort(a.begin(), a.end());
for (int i = 1; i < (int)a.size(); ++i)
if (a[i - 1] == a[i...
Educational Codeforces Round 171 Editorial, Разбор Educational Codeforces Round 171, Idea: [user:BledDest,2024-10-29], Idea: [user:adedalic,2024-10-29], Idea: [user:shnirelman,2024-10-29], Идея: [user:BledDest,2024-10-29], Идея: [user:adedalic,2024-10-29], Идея: [user:shnirelman,2024-10-29]
123.
Educational Codeforces Round 80 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1288] [contest:1288] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-01-13] Glazov, Adilbek [user:adedalic,2020-01-13] Dalabaev, Vladimir [user:Vovuh,2020-01-13] Petrov, Ivan [user:Bl...
Educational Codeforces Round 80 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 80 (Rated for Div. 2)
124.
Educational Codeforces Round 56 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1093] [contest:1093] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ACM ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Ajosteen,2018-12-14] Glazov, Adilbek [user:adedalic,2018-12-14] Dalabaev, Vladimir [user:Vovuh,2018-12-14] Petrov, Ivan...
Educational Codeforces Round 56 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 56 (Rated for Div. 2)
125.
Educational Codeforces Round 83 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1312] [contest:1312] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-03-08] Glazov, Adilbek [user:adedalic,2020-03-08] Dalabaev, Vladimir [user:vovuh,2020-03-08] Petrov, Ivan [user:Bl...
Educational Codeforces Round 83 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
126.
Educational Codeforces Round 76 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1257] [contest:1257] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-10-23] Glazov, Adilbek [user:adedalic,2019-10-23] Dalabaev, Vladimir [user:Vovuh,2019-10-23] Petrov, Ivan [user:Bl...
Educational Codeforces Round 76 [Rated for Div. 2], Educational Codeforces Round 76 [рейтинговый для Div. 2], The problems were invented and prepared by Roman [user:Roms,2019-10-23] Glazov,
Adilbek, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Задачи вместе со мной придумывали и готовили Роман [user:Roms,2019-10-23]
Глазов, Адилбек
Announcement of Educational Codeforces Round 76 (Rated for Div. 2)
127.
Educational Codeforces Round 127 Editorial [problem:1671A]
Idea: [user:BledDest,2022-04-23]
<spoiler summary="Tutorial">
[tutorial:1671A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
s = input()
ans = True
n = len(s)
for j in range(n):
if (j == 0 or s[j] != s[j - 1]) and (j == n - 1 or s[j] != s[j + 1]):
ans = False
print('YES' if ans else 'NO')
~~~~~
</spoiler>
[problem:1671B]
Idea: [user:vovuh,2022-04-23]
<spoiler summary="Tutorial">
[tutorial:1671B]
</spoiler>
<spoiler summary="Solution (vovuh)">
~~~~~
for i in range(int(input())):
n = int(input())
x = list(map(int, input().split()))
print('YES' if x[-1] - x[0] - n + 1 <= 2 else 'NO')
~~~~~
</spoiler>
[problem:1671C]
Idea: [user:vovuh,2022-04-23] and [user:BledDest,2022-04-23]
<spoiler summary="Tutorial">
[tutorial:1671C]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
fun main() {
repeat(rea...
Educational Codeforces Round 127 Editorial, Разбор Educational Codeforces Round 127, ] = 6; cnt[5][3][9] = 4; cnt[5][4][10] = 1; cnt[6][1][5] = 5; cnt[6][1][6] = 3
128.
Educational Codeforces Round 144 Editorial [problem:1796A]
Idea: [user:BledDest,2023-03-01]
<spoiler summary="Tutorial">
[tutorial:1796A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main()
{
string fb;
int cur = 1;
while(fb.size() < 100)
{
if(cur % 3 == 0) fb += "F";
if(cur % 5 == 0) fb += "B";
cur++;
}
int t;
cin >> t;
for(int i = 0; i < t; i++)
{
int k;
cin >> k;
string s;
cin >> s;
cout << (fb.find(s) != string::npos ? "YES" : "NO") << endl;
}
}
~~~~~
</spoiler>
[problem:1796B]
Idea: [user:BledDest,2023-03-01]
<spoiler summary="Tutorial">
[tutorial:1796B]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
a = input()
b = input()
if a[0] == b[0]:
print("YES")
print(a[0] + "*")
continue
if a[-1] == b[-1]:
print("Y...
Educational Codeforces Round 144 Editorial, Разбор Educational Codeforces Round 144, vector pw(10); pw[0] = 1; for (int i = 1; i < 10; ++i) pw[i] = pw[i - 1] * 10;
129.
Codeforces Round #839 (Div. 3) Привет, Codeforces!
On [contest_time:1772], [contest:1772] will start. This is a usual round for the participants from the third division. The round will contain 7 problems, which are mostly suited for participants with rating below 1600 (or we hope so). Although, as usual, participants with rating of 1600 and greater can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them. The penalty for a wrong submission is equal to **10 minutes**.
[We remind you](https://codeforces.me/blog/entry/59228) that only the _trusted participants of the third division_ will be included in the official standings table. As it is written on the blog which you can access by this link, this is a compulsory measure for combating unspor...
Codeforces Round #839 (Div. 3), rules of educational rounds (extended ICPC). Thus, during the round, solutions
will be judged on
Announcement of Codeforces Round 839 (Div. 3)
130.
Educational Codeforces Round 115 Editorial [problem:1598A]
Idea: [user:BledDest,2021-10-11]
<spoiler summary="Tutorial">
[tutorial:1598A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
def solve():
n = int(input())
s1 = input()
s2 = input()
bad = False
for i in range(n):
bad |= s1[i] == '1' and s2[i] == '1'
if bad:
print('NO')
else:
print('YES')
t = int(input())
for i in range(t):
solve()
~~~~~
</spoiler>
[problem:1598B]
Idea: [user:fcspartakm,2021-10-11]
<spoiler summary="Tutorial">
[tutorial:1598B]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
n = int(input())
a = [[] for i in range(n)]
for j in range(n):
a[j] = list(map(int, input().split()))
ans = False
for j in range(5):
for k in range(5):
if k != j:
cnt1 = 0
cnt2 = 0
cntno = 0
for z in range(n):
if a[z][j] =...
Educational Codeforces Round 115 Editorial, Разбор Educational Codeforces Round 115, Idea: [user:BledDest,2021-10-11], Idea: [user:fcspartakm,2021-10-11], pw[0] = get(1); forn(i, N - 1) pw[i + 1] = pw[i] * get(10); sum[0] = get(0);
forn(i, n, Идея: [user:BledDest,2021-10-11], Идея: [user:fcspartakm,2021-10-11]
131.
Codeforces Round #881 (Div. 3) Hello, Codeforces!
On [contest_time:1843] [contest:1843] will start.
You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the *trusted participants of the third division* will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a *trusted partic...
Codeforces Round #881 (Div. 3), register for the round unofficially. The round will be hosted by rules of
educational rounds
Announcement of Codeforces Round 881 (Div. 3)
132.
Codeforces Round #650 (Div. 3) Hello, Codeforces!
\<almost-copy-pasted-part>
Hello! [contest:1367] will start at [contest_time:1367]. You will be offered 6 problems (one of them will have subtasks) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. We tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third ...
Codeforces Round #650 (Div. 3), . The round will be hosted by rules of educational rounds (extended ACM-ICPC).
Thus, during theround
Announcement of Codeforces Round 650 (Div. 3)
133.
Codeforces Round 1017 (Div. 4) # Good Morning/Afternoon/Evening/Night Codeforces
----------
<center>
<br/>
<img src="https://i.ibb.co/dZM4Rgm/1000015885-removebg-preview.png" alt="1000015885-removebg-preview" border="0"><br/>
This is Orangutini Ananasini Emoji
</center>
----------
[user:cry,2025-04-07] and I are overjoyed to welcome you to participate in [contest:2094] at [contest_time:2094]. **Note the unusual time of the round**. You will be given $2$ hours and $15$ minutes to solve $8$ problems.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**. After open hacks all accepted solutions will be rejudged on successful hacks.
Note that the **penalty** for each wrong submission in this round is **10 minutes**. Also, **note the [rule restricting AI use](https://codeforces.me/blog/entry/133941)!!!** If you are caught using AI, your submissio...
Codeforces Round 1017 (Div. 4), round will be hosted by rules of educational rounds (extended ICPC). Thus,
solutions will be judged on
Announcement of Codeforces Round 1017 (Div. 4)
134.
Educational Codeforces Round 72 Editorial [problem:1217A]
<spoiler summary="Tutorial">
[tutorial:1217A]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
fun main() {
val t = readLine()!!.toInt()
for (ct in 1..t) {
val (str, int, exp) = readLine()!!.split(' ').map { it.toInt() }
val minAddStr = maxOf(0, (exp + int - str + 2) / 2)
println(maxOf(exp - minAddStr + 1, 0))
}
}
~~~~~
</spoiler>
[problem:1217B]
Idea: [user:Roms,2019-09-06]
<spoiler summary="Tutorial">
[tutorial:1217B]
</spoiler>
<spoiler summary="Solution (Roms)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
const int N = 105;
int t;
int n, m;
int d[N], h[N];
int main() {
cin >> t;
for(int tc = 0; tc < t; ++tc){
cin >> n >> m;
int maxDH = -2e9;
for(int i = 0; i < n; ++i){
cin >> d[i] >> h[i];
maxDH = max(maxDH, d[i] - h[i]);
}
int res = 1;
int maxD = *max_element(d, d + n);
m -= maxD;
if(m > 0){
if(maxDH <= 0) res = -1;...
Educational Codeforces Round 72 Editorial, Разбор Educational Codeforces Round 72, const int BUF = 10 * 1000 * 1000 + 13; const int N = 300 * 1000 + 13; const int
M = 300 * 1000, void upd(node &t, int val){ int x = val; forn(i, LOGN){ if (x % 10 != 0) t[i] =
min(t[i
135.
Educational Codeforces Round 156 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1886] [contest:1886] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="https://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-10-08] Dalabaev, Ivan [user:BledDest,2023-10-08] Androsov, Maksim [user:Neon,2023-10-08] Mesch...
Educational Codeforces Round 156 [Rated for Div. 2], Educational Codeforces Round 156 [рейтинговый для Div. 2], Hello Codeforces! On [contest_time:1886] [contest:1886] will start. Series of
Educational, The problems were invented and prepared by Adilbek [user:adedalic,2023-10-08]
Dalabaev, Ivan, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Задачи вместе со мной придумывали и готовили Адилбек [user:adedalic,2023-10-08]
Далабаев, Иван
Announcement of Educational Codeforces Round 156 (Rated for Div. 2)
136.
Educational Codeforces Round 154 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1861] [contest:1861] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="https://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-08-30] Dalabaev, Ivan [user:BledDest,2023-08-30] Androsov, Maksim [user:Neon,2023-08-30] Mesch...
Educational Codeforces Round 154 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 154 (Rated for Div. 2)
137.
How not to read problem statements I wanted to write super-harsh blog but then I decided to split it into educational part and whining part. This is whining part. To read some cool stuff go [here](https://codeforces.me/blog/entry/62730). This one will also be educational on a slightly different topic. And there will be A LOT of harsh stuff.
I'm not saying that I'm perfect. That round had some really bad problemsetting issues. Problem E was googleable, problem D had very weak tests against very stupid solution (so stupid that none of the authors and testers come up with it, moreover, it is so counter-intuitive that I don't know how so many people independently did it). In two constructive problems participants could look at jury's output, the feature of which I didn't know. And I'm sorry for these issues. BUT. [This comment](https://codeforces.me/blog/entry/62614#comment-466588) has very negative rating despite being so true. And no one are here to back me up. So I want to speak my truth as I always do.
Let me ac...
-10-26]. [Problem C from 2nd division of CF Round
#518](https://codeforces.me/contest/1068
138.
Educational Codeforces Round 130 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1697] [contest:1697] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-06-11] Dalabaev, Vladimir [user:vovuh,2022-06-11] Petrov, Ivan [user:BledDest,2022-06-11] Androsov, Mak...
Educational Codeforces Round 130 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 130 (Rated for Div. 2)
139.
Educational Codeforces Round 44 [Rated for Div. 2] Hello Codeforces!
On [contest_time:985] Educational Codeforces Round 44 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by Adilbek [user:adedalic,2018-05-20] Dalabaev, Vladimir [user:Vovuh,2018-05-20] Petrov and me.
Good luck to all participants!
Congratulations to the winners:
<table class='bordertable'>
<tbody>
<tr>
<th>Rank</th>
...
Educational Codeforces Round 44 [Rated for Div. 2], Hello Codeforces! On [contest_time:985] Educational Codeforces Round 44 will
start. Series
Announcement of Educational Codeforces Round 44 (Rated for Div. 2)
140.
Codeforces Round #644 (Div. 3) Hello, Codeforces!
We have planned this round as a Div. 4, but testing showed us, that problems are more suitable for Div. 3. **Therefore, instead of the previously announced Div. 4 we will hold Div. 3 round**.
\<almost-copy-pasted-part\>
Hello! [Codeforces Round #644 (Div. 3)](https://codeforces.me/contest/1360) will start at [contest_time:1360]. You will be offered 8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 8 problems and 2 hours to solve them.
Not...
Codeforces Round #644 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ACM-ICPC). Thus
Announcement of Codeforces Round 644 (Div. 3)
141.
Educational Codeforces Round 69 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1197] [contest:1197] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-07-13] Glazov, Adilbek [user:adedalic,2019-07-13] Dalabaev, Vladimir [user:Vovuh,2019-07-13] Petrov, Ivan [user:Bl...
Educational Codeforces Round 69 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
142.
Educational Codeforces Round 63 Editorial [problem:1155A]
<spoiler summary="Tutorial">
[tutorial:1155A]
</spoiler>
<spoiler summary="Solution (Vovuh)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
#ifdef _DEBUG
freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
#endif
int n;
string s;
cin >> n >> s;
for (int i = 1; i < int(s.size()); ++i) {
if (s[i] < s[i - 1]) {
cout << "YES" << endl;
cout << i << " " << i + 1 << endl;
return 0;
}
}
cout << "NO" << endl;
return 0;
}
~~~~~
</spoiler>
[problem:1155B]
<spoiler summary="Tutorial">
[tutorial:1155B]
</spoiler>
<spoiler summary="Solution (Roms)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
int n;
string s;
int main(){
cin >> n >> s;
int cnt1 = (n - 11) / 2;
int cnt2 = cnt1;
string res = "";
for(int i = 0; i < n; ++i){
if(s[i] == '8'){
if(cnt1 > 0) --cnt1;
else res += s[i];
...
Educational Codeforces Round 63 Editorial, Разбор Educational Codeforces Round 63, int k = 10; vector f;
143.
Educational Codeforces Round 170 Editorial [problem:2025A]
Idea: [user:BledDest,2024-10-15]
<spoiler summary="Tutorial">
[tutorial:2025A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
for _ in range(int(input())):
s = input()
t = input()
lcp = 0
n = len(s)
m = len(t)
for i in range(1, min(n, m) + 1):
if s[:i] == t[:i]:
lcp = i
print(n + m - max(lcp, 1) + 1)
~~~~~
</spoiler>
[problem:2025B]
Idea: [user:adedalic,2024-10-15]
<spoiler summary="Tutorial">
[tutorial:2025B]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
const int MOD = int(1e9) + 7;
int main() {
int t; cin >> t;
vector<int> ks(t);
for (int _ = 0; _ < 2; _++)
for (int i = 0; i < t; i++)
cin >> ks[i];
vector<int> ans(1 + *max_element(ks.begin(), ks.end()), 1);
for (int i = 1; i < (int)ans.size(); i++)
ans[i] = (2LL * ans[i - 1]) % MOD;
for (int k : ks)
cout << ans[k] << '\n';
return 0;
}
~~~~~
</spoi...
Educational Codeforces Round 170 Editorial, Разбор Educational Codeforces Round 170, Idea: [user:BledDest,2024-10-15], Idea: [user:adedalic,2024-10-15], Idea: [user:fcspartakm,2024-10-15], const int p = sqrt(m + 10); const int siz = (m + p - 1) / p;, Идея: [user:BledDest,2024-10-15], Идея: [user:adedalic,2024-10-15], Идея: [user:fcspartakm,2024-10-15]
144.
Educational Codeforces Round 58 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1101] [contest:1101] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ACM ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-01-10] Glazov, Adilbek [user:adedalic,2019-01-10] Dalabaev, Vladimir [user:Vovuh,2019-01-10] Petrov, Ivan [us...
Educational Codeforces Round 58 [Rated for Div. 2], Educational Codeforces Round 58 [рейтинговый для Div. 2], The problems were invented and prepared by Roman [user:Roms,2019-01-10] Glazov,
Adilbek, This round will be **rated for the participants with rating lower than 2100**.
It will be held on, Задачи вместе со мной придумывали и готовили Роман [user:Roms,2019-01-10]
Глазов, Адилбек
Announcement of Educational Codeforces Round 58 (Rated for Div. 2)
145.
Quick unofficial editorial for Educational Round 59 (Div. 2) Continuing with the theme from last time, here's a quick writeup of my approaches:
#### [problem:1107A]
Since we just want to make two numbers such that the first number is smaller than the second, our best bet is to use only the first digit for the first number and the rest of the digits for the second number. Note that since the numbers can have up to 300 digits we shouldn't actually evaluate the second number. Instead, since the digits only include 1 through 9, we can handle that case by checking the number of digits. Code: [submission:49002957]
#### [problem:1107B]
The key observation is that the digital root of an integer $k$ is the single-digit number $1 \leq d \leq 9$ such that $k \equiv d \bmod 9$. You can prove this by noticing that $10^p \equiv 1 \bmod 9$ for all $p$. Once we observe this, finding the $k$-th number is very simple; see the code: [submission:48993705]
#### [problem:1107C]
Since we are only allowed to push the same button $k$ times in a row, let's do...
Quick unofficial editorial for Educational Round 59 (Div. 2), $10^p \equiv 1 \bmod 9$ for all $p$. Once we observe this, finding the $k$-th
number is very simple
146.
Codeforces: Results of 2018 Hi Codeforces!
February 2019 is already on the calendar, which means that I was late with the report for 2018. Better late than
never! Let's remember last year.
In 2018, [user:_kun_,2019-02-05], [user:300iq,2019-02-05] and [user:arsijo,2019-02-05] joined the team of coordinators. The work of the coordinators is headed
(and is the coordinator of the coordinators) [user:KAN,2019-02-05]. I really hope that a more measured schedule of preparing rounds by
a large team of coordinators will give a better insight into the contests. The main innovations in the platform are implemented
by me and the developers [user:kuviman,2019-02-05], [user:fcspartakm,2019-02-05], [user:MaximShipko,2019-02-05]. Great work on the organization of events and
prizes mailing was done by [user:gKseni,2019-02-05].
Special thanks to the writers of the problems and testers. It is your content that charges the community with life and unites
all of us. Thank you for the problems!
And now let's summarize...
** and personally Pavel Durov is supporting Codeforces activities for many
years, every regularround is
147.
Codeforces Round 995 (Div. 3) Hello, Codeforces!
On [contest_time:2051] the [contest:2051] will start. The round will contain 7 problems, which are mostly suited for participants with rating below 1600 (or we hope so). Although, as usual, participants with rating of 1600 and greater can register for the round unofficially. Participants with rating below 1600 can also use unrated registration to participate unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks (we hope that our tests are strong enough, so there won't be too many solutions hacked during this phase).
You will have to solve **7 problems** in **2 hours and 15 minutes**. The penalty for a wrong submission is equal to **10 minutes**.
[We remind you](https://codeforces.me/blog/entry/59228) that only _the trusted participants of the third division_ will be included in the offic...
Codeforces Round 995 (Div. 3), . The round will be hosted by rules of educational rounds (extended ACM-ICPC).
Thus, during theround
Announcement of Codeforces Round 995 (Div. 3)
148.
Educational Codeforces Round 173 Editorial [problem:2043A]
Idea: [user:BledDest,2024-12-25]
<spoiler summary="Tutorial">
[tutorial:2043A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
n = int(input())
ans = 1
while n > 3:
n //= 4
ans *= 2
print(ans)
~~~~~
</spoiler>
[problem:2043B]
Idea: [user:AcidWrongGod,2024-12-25]
<spoiler summary="Tutorial">
[tutorial:2043B]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
import sys
sys.set_int_max_str_digits(6000)
def fact(x):
if x == 0:
return 1
return x * fact(x - 1)
t = int(input())
for i in range(t):
n, k = map(int, input().split())
n = min(n, 7)
s = int(str(k) * fact(n))
for i in range(1, 10, 2):
if s % i == 0:
print(i, end = ' ')
print()
~~~~~
</spoiler>
[problem:2043C]
Idea: [user:Ferume,2024-12-25]
<spoiler summary="Tutorial">
[tutorial:2043C]
</spoiler>
<...
Educational Codeforces Round 173 Editorial, Разбор Educational Codeforces Round 173, , r1 = 0, 0 l2, r2 = 2*10**9, -2*10**9
149.
Educational Codeforces Round 121 Editorial [problem:1626A]
Idea: [user:BledDest,2022-01-17]
<spoiler summary="Tutorial">
[tutorial:1626A]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
print(''.join(sorted(input())))
~~~~~
</spoiler>
[problem:1626B]
Idea: [user:BledDest,2022-01-17]
<spoiler summary="Tutorial">
[tutorial:1626B]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
x = [ord(c) - ord('0') for c in input()]
n = len(x)
for i in range(n - 2, -1, -1):
if x[i] + x[i + 1] >= 10:
x[i + 1] += x[i] - 10
x[i] = 1
break
else:
x[1] += x[0]
x.pop(0)
print(''.join([chr(c + ord('0')) for c in x]))
~~~~~
</spoiler>
[problem:1626C]
Idea: [user:BledDest,2022-01-17]
<spoiler summary="Tutorial">
[tutorial:1626C]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
n = int(input())
k = list(map(int, input().split()))
h = ...
Educational Codeforces Round 121 Editorial, Разбор Educational Codeforces Round 121, ) for i in range(n - 2, -1, -1): if x[i] + x[i + 1] >= 10: x[i + 1] += x[i] - 10
x[i
150.
Educational Codeforces Round 157 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1895] [contest:1895] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="https://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-11-02] Dalabaev, Ivan [user:BledDest,2023-11-02] Androsov, Maksim [user:Neon,2023-11-02] Mesch...
Educational Codeforces Round 157 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 157 (Rated for Div. 2)
151.
VK Cup 2018 — Wild-card Round 1 Hi!
Tomorrow, on [March 17th, 2018, at 15:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=VK+Cup+Wild-card+Round+1&iso=20180317T1835&p1=166&ah=2) the first Wild-card Round of VK Cup 2018 will be held. Along with it we will host a parallel unofficial round in which everyone can take part.
The rounds will use **special rules, the rounds will be unrated.** The problems were prepared by Codeforces team: [user:fcspartakm,2018-03-16], [user:MikeMirzayanov,2018-03-16] and me. Thanks to [user:Vovuh,2018-03-16], [user:GreenGrape,2018-03-16], [user:neckbosov,2018-03-16], [user:glebodin,2018-03-16] and [user:gritukan,2018-03-16] for testing the round and their help to make the round better!
The detailed rules will be added to this post around 30 minutes before the start. There will be 24-hours open hacks phase after the round, like in Codeforces Educational Rounds.
**Round rules:**
The round will be almost usual contest with ACM ICPC rules. There will be 10 proble...
VK Cup 2018 — Wild-card Round 1, The round will be almost usual contest with ACM ICPC rules. There will be 10
problems for 2 hours
Announcement of VK Cup 2018 - Wild-card Round 1
Announcement of VK Cup 2018 - Wild-card Round 1 (unofficial unrated mirror)
152.
Eolymp Cup #2 
Eolymp Cup #2
=============
We are very excited to announce [the second round of Eolymp Cup](https://basecamp.eolymp.com/en/contests/ptmnufrm6p6nl7gods1loo65go) on **6th of October at 15.00 UTC**! Take up a challenge to get a chance to win a trophy, medals, prizes, and scholarships at [Harbour.Space University](https://harbour.space/).
**Eolymp Cup** is a programming competition for students. The competition consists of 4 rounds, held throughout the year. Each round features 6 problems, each designed to challenge participants' knowledge of algorithms, data structures and programming.
The competition is open to everyone, but prizes will only be awarded to participants who are born after January 1, 2002. All other participants will compete unofficially.
### Registration
You can register on the [contest page](https://basecamp.eolymp.com/en/contests/ptmnufrm6p6nl7gods1loo65go), just click "Joi...
each round, the top 10 institutions as well as 10 randomly selected
institutions among these who scored
153.
Educational Codeforces Round 188 Editorial [problem:2204A]
Idea: [user:BledDest,2026-03-17]
<spoiler summary="Tutorial">
[tutorial:2204A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin >> t;
for(int i = 0; i < t; i++)
{
int n;
cin >> n;
string s;
cin >> s;
cout << s.find("RL") + 2 << endl;
}
return 0;
}
~~~~~
</spoiler>
[problem:2204B]
Idea: [user:fcspartakm,2026-03-17]
<spoiler summary="Tutorial">
[tutorial:2204B]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
void solve()
{
int n;
cin >> n;
vector<int> a(n);
for(int i = 0; i < n; i++) cin >> a[i];
int mx = 0;
int ans = 0;
for(int i = 0; i < n; i++)
{
if(a[i] >= mx) ans++;
mx = max(mx, a[i]);
}
cout << ans << "\n";
}
int main()
{
...
Educational Codeforces Round 188 Editorial, Разбор Educational Codeforces Round 188, int f(int x) { int res = 0; while(x != 0) { res += x % 10; x
154.
Educational Codeforces Round 148 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1832] [contest:1832] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-05-11] Dalabaev, Ivan [user:BledDest,2023-05-11] Androsov, Maksim [user:Neon,2023-05-11] Mesche...
Educational Codeforces Round 148 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 148 (Rated for Div. 2)
155.
Educational Codeforces Round 150 Editorial [problem:1841A]
Idea: [user:BledDest,2023-06-13]
<spoiler summary="Tutorial">
[tutorial:1841A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
n = int(input())
print('Alice' if n >= 5 else 'Bob')
~~~~~
</spoiler>
[problem:1841B]
Idea: [user:BledDest,2023-06-13]
<spoiler summary="Tutorial">
[tutorial:1841B]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
q = int(input())
a = []
cnt = 0
for x in map(int, input().split()):
nw_cnt = cnt + (len(a) > 0 and a[-1] > x)
if nw_cnt == 0 or (nw_cnt == 1 and x <= a[0]):
a.append(x)
cnt = nw_cnt
print('1', end="")
else:
print('0', end="")
print()
~~~~~
</spoiler>
[problem:1841C]
Idea: [user:BledDest,2023-06-13]
<spoiler summary="Tutorial">
[tutorial:1841C]
</spoiler>
<spoiler summary="Solution 1 (Neon)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
const ...
Educational Codeforces Round 150 Editorial, Разбор Educational Codeforces Round 150, ) if max_id > i: ans -= 10 ** i else: ans += 10 ** i, const int val[] = {1, 10, 100, 1000, 10000}; const int INF = 1e9;
156.
Educational Codeforces Round 112 Editorial [problem:1555A]
Idea: [user:BledDest,2021-07-31]
<spoiler summary="Tutorial">
[tutorial:1555A]
</spoiler>
<spoiler summary="Solution (Neon)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
int t;
cin >> t;
while (t--) {
long long n;
cin >> n;
cout << max(6LL, n + 1) / 2 * 5 << '\n';
}
}
~~~~~
</spoiler>
[problem:1555B]
Idea: [user:adedalic,2021-07-31]
<spoiler summary="Tutorial">
[tutorial:1555B]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
#define fore(i, l, r) for(int i = int(l); i < int(r); i++)
#define sz(a) int((a).size())
#define x first
#define y second
typedef long long li;
typedef pair<int, int> pt;
const int INF = int(1e9);
int W, H;
int x1, y1, x2, y2;
int w, h;
inline bool read() {
if(!(cin >> W >> H))
return false;
cin >> x1 >> y1 >> x2 >> y2;
cin >> w >> h;
return true;
}
inline void solv...
Educational Codeforces Round 112 Editorial, Разбор Educational Codeforces Round 112, const int INF = 2e9 + 10;
157.
Educational Codeforces Round 126 Editorial [problem:1661A]
Idea: [user:BledDest,2022-04-10]
<spoiler summary="Tutorial">
[tutorial:1661A]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
import kotlin.math.abs
fun sum(a1: Int, a2: Int, b1: Int, b2: Int) = abs(a1 - a2) + abs(b1 - b2)
fun main() {
repeat(readLine()!!.toInt()) {
val n = readLine()!!.toInt()
val a = readLine()!!.split(' ').map { it.toInt() }.toIntArray()
val b = readLine()!!.split(' ').map { it.toInt() }.toIntArray()
var sum = 0L
for (i in 1 until n) {
if (sum(a[i - 1], a[i], b[i - 1], b[i]) > sum(a[i - 1], b[i], b[i - 1], a[i]))
a[i] = b[i].also { b[i] = a[i] }
sum += sum(a[i - 1], a[i], b[i - 1], b[i])
}
println(sum)
}
}
~~~~~
</spoiler>
[problem:1661B]
Idea: [user:adedalic,2022-04-10]
<spoiler summary="Tutorial">
[tutorial:1661B]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
fun main(...
Educational Codeforces Round 126 Editorial, Разбор Educational Codeforces Round 126, Idea: [user:BledDest,2022-04-10], Idea: [user:adedalic,2022-04-10], Idea: [user:vovuh,2022-04-10], Идея: [user:BledDest,2022-04-10], Идея: [user:adedalic,2022-04-10], Идея: [user:vovuh,2022-04-10]
158.
Educational Codeforces Round 83 Editorial [problem:1312A]
Idea: [user:BledDest,2020-03-10]
<spoiler summary="Tutorial">
[tutorial:1312A]
</spoiler>
<spoiler summary="Solution (vovuh)">
~~~~~
for i in range(int(input())):
n, m = map(int, input().split())
print('YES' if n % m == 0 else 'NO')
~~~~~
</spoiler>
[problem:1312B]
Idea: [user:Roms,2020-03-10]
<spoiler summary="Tutorial">
[tutorial:1312B]
</spoiler>
<spoiler summary="Solution (Roms)">
~~~~~
for t in range(int(input())):
n = input()
print(*sorted(map(int, input().split()))[::-1])
~~~~~
</spoiler>
[problem:1312C]
Idea: [user:adedalic,2020-03-10]
<spoiler summary="Tutorial">
[tutorial:1312C]
</spoiler>
<spoiler summary="Solution 1 (adedalic)">
~~~~~
fun main() {
val T = readLine()!!.toInt()
testCases@for (tc in 1..T) {
val (_, k) = readLine()!!.split(' ').map { it.toLong() }
val a = readLine()!!.split(' ').map { it.toLong() }.toLongArray()
var maxPower ...
Educational Codeforces Round 83 Editorial, Разбор Educational Codeforces Round 83, Idea: [user:adedalic,2020-03-10] and [user:BledDest,2020-03-10], Идея: [user:adedalic,2020-03-10] и [user:BledDest,2020-03-10]
159.
Codeforces Round 895 (Div. 3) Hello Codeforces! [contest:1872] will start at [contest_time:1872]. You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228), that only the _trusted participants of the third division_ will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a _trusted participant of t...
Codeforces Round 895 (Div. 3), for the round unofficially. The round will be hosted by rules of educational
rounds (extended ICPC
Announcement of Codeforces Round 895 (Div. 3)
160.
Educational Codeforces Round 122 — Editorial [problem:1633A]
Idea: [user:BledDest,2022-02-01], preparation: [user:BledDest,2022-02-01]
<spoiler summary="Tutorial">
[tutorial:1633A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
n = int(input())
if n % 7 == 0:
print(n)
else:
ans = -1
for j in range(10):
if (n - n % 10 + j) % 7 == 0:
ans = n - n % 10 + j
print(ans)
~~~~~
</spoiler>
[problem:1633B]
Idea: [user:BledDest,2022-02-01], preparation: [user:awoo,2022-02-01] and [user:Neon,2022-02-01]
<spoiler summary="Tutorial">
[tutorial:1633B]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
s = input()
print(min((len(s) - 1) // 2, s.count('0'), s.count('1')))
~~~~~
</spoiler>
[problem:1633C]
Idea: [user:BledDest,2022-02-01], preparation: [user:Neon,2022-02-01]
<spoiler summary="Tutorial">
[tutorial:1633C]
</spoil...
Educational Codeforces Round 122 — Editorial, Разбор Educational Codeforces Round 122, : print(n) else: ans = -1 for j in range(10): if (n - n % 10 + j) % 7
161.
Codeforces Round #828 (Div. 3) Hello! [contest:1744] will start at [contest_time:1744]. You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **6-8 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a _trusted participant of the thi...
Codeforces Round #828 (Div. 3), round unofficially. The round will be hosted by rules of educational rounds
(extended ICPC). Thus
Announcement of Codeforces Round 828 (Div. 3)
162.
Educational Codeforces Round 97 Editorial [problem:1437A]
Idea: [user:adedalic,2020-10-28]
<spoiler summary="Tutorial">
[tutorial:1437A]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
fun main() {
repeat(readLine()!!.toInt()) {
val (l, r) = readLine()!!.split(' ').map { it.toInt() }
println(if (2 * l > r) "YES" else "NO");
}
}
~~~~~
</spoiler>
[problem:1437B]
Idea: [user:adedalic,2020-10-28]
<spoiler summary="Tutorial">
[tutorial:1437B]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
#define fore(i, l, r) for(int i = int(l); i < int(r); i++)
#define sz(a) int((a).size())
const int INF = int(1e9);
int n;
string s;
inline bool read() {
if(!(cin >> n >> s))
return false;
return true;
}
int cntSame(const string &s) {
int ans = 0;
fore (i, 1, sz(s))
ans += (s[i - 1] == s[i]);
assert(ans % 2 == 0);
return ans / 2;
}
inline void solve() {
int ans = INF;
fore (...
Educational Codeforces Round 97 Editorial, Разбор Educational Codeforces Round 97, Idea: [user:BledDest,2020-10-28], Idea: [user:Ne0n25,2020-10-28], Idea: [user:adedalic,2020-10-28], Идея: [user:BledDest,2020-10-28], Идея: [user:Ne0n25,2020-10-28], Идея: [user:adedalic,2020-10-28]
163.
Codeforces Round #636 (Div. 3) <almost-copy-pasted-part>
Hello!
[contest:1343] will start at [contest_time:1343]. You will be offered 6 or 7 problems (or 8) with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ACM-ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 6 or 7 (or 8) problems and 2 hours to solve them.
Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**.
[Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the ...
Codeforces Round #636 (Div. 3), educational rounds (extended ACM-ICPC). Thus, during the round, solutions will
be judged on
Announcement of Codeforces Round 636 (Div. 3)
164.
Educational Codeforces Round 57 Editorial [problem:1096A]
<spoiler summary="Tutorial">
[tutorial:1096A]
</spoiler>
<spoiler summary="Solution (PikMike)">
~~~~~
T = int(input())
for i in range(T):
l, r = map(int, input().split())
print(l, l * 2)
~~~~~
</spoiler>
[problem:1096B]
<spoiler summary="Tutorial">
[tutorial:1096B]
</spoiler>
<spoiler summary="Solution (Vovuh)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
#ifdef _DEBUG
freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
#endif
int n;
string s;
cin >> n >> s;
int cntl = 0, cntr = 0;
for (int i = 0; i < n; ++i) {
if (s[i] == s[0]) {
++cntl;
} else {
break;
}
}
for (int i = n - 1; i >= 0; --i) {
if (s[i] == s[n - 1]) {
++cntr;
} else {
break;
}
}
if (s[0] == s[n - 1]) {
cout << ((cntl + 1) * 1ll * (cntr + 1)) % 998244353 << endl;
} else {
cout << (cntl + cntr + 1) % 998244353;
}
return 0;
}
~~~~~
</spoiler>
...
Educational Codeforces Round 57 Editorial, Разбор Educational Codeforces Round 57, const int MOD = 998244353; const int N = 10 * 1000 + 7; const int M = 100 + 7;, vector ans(1, 1); vector f(10, 0); forn(i, k) f[a[i]] = 1;
165.
Educational Codeforces Round 124 Editorial [problem:1651A]
Idea: [user:BledDest,2022-03-11]
<spoiler summary="Tutorial">
[tutorial:1651A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
n = int(input())
print(2 ** n - 1)
~~~~~
</spoiler>
[problem:1651B]
Idea: [user:adedalic,2022-03-11]
<spoiler summary="Tutorial">
[tutorial:1651B]
</spoiler>
<spoiler summary="Solution (awoo)">
~~~~~
for _ in range(int(input())):
n = int(input())
if 3**(n-1) > 10**9:
print("NO")
else:
print("YES")
print(*[3**x for x in range(n)])
~~~~~
</spoiler>
[problem:1651C]
Idea: [user:adedalic,2022-03-11]
<spoiler summary="Tutorial">
[tutorial:1651C]
</spoiler>
<spoiler summary="Solution (adedalic)">
~~~~~
#include<bits/stdc++.h>
using namespace std;
#define fore(i, l, r) for(int i = int(l); i < int(r); i++)
typedef long long li;
const int INF = int(1e9);
int n;
vector<int> a, b;
inline bool read() {
if(!(ci...
Educational Codeforces Round 124 Editorial, Разбор Educational Codeforces Round 124, int bestCandidate(const vector &vals, int cur) { int bst = INF + 10, pos = -1;
fore (i, 0, ~~~~~ for _ in range(int(input())): n = int(input()) if 3**(n-1) > 10**9:
print("NO
166.
EPIC Institute of Technology Round Summer 2024 (Div. 1 + Div. 2) <a href="https://epic-institute.io/"><img alt="EPIC" src="https://assets.codeforces.com/images/deltix/2_logo.gif" style="float:right; height: 154px; padding-left: 35px; padding-right: 73px; padding-top: 41px; padding-bottom: 33px;"/></a>
Hi, Codeforces!
We are pleased to invite you to [contest:1987], which will be held on [contest_time:1987]. You will be given **8 problems**, two of which are divided into two subtasks, and you will have **3 hours** to solve them. The round will be rated for **everyone**.
At least one of the problems will be interactive, so please read the [guide for interactive problems](https://codeforces.me/blog/entry/45307) if you are not familiar with it.
We would like to thank:
- [user:errorgorn,2024-06-27] for coordinating the round.
- [user:Geothermal,2024-06-27], [user:turmax,2024-06-27], [user:noimi,2024-06-27], [user:SomethingNew,2024-06-27], [user:feecIe6418,2024-06-27], [user:Endagorion,2024-06-27], [user:glebustim,2024-06-27], [user:zelibo...
EPIC Institute of Technology Round Summer 2024 (Div. 1 + Div. 2), are divided into two subtasks, and you will have **3 hours** to solve them. The
round will be rated
Announcement of EPIC Institute of Technology Round Summer 2024 (Div. 1 + Div. 2)
167.
Educational Codeforces Round 84 Editorial [problem:1327A]
Idea: [user:vovuh,2020-03-24]
<spoiler summary="Tutorial">
[tutorial:1327A]
</spoiler>
<spoiler summary="Solution (vovuh)">
~~~~~
for i in range(int(input())):
n, k = map(int, input().split())
print('YES' if k * k <= n and n % 2 == k % 2 else 'NO')
~~~~~
</spoiler>
[problem:1327B]
Idea: [user:BledDest,2020-03-24]
<spoiler summary="Tutorial">
[tutorial:1327B]
</spoiler>
<spoiler summary="Solution (pikmike)">
~~~~~
from sys import stdin, stdout
t = int(stdin.readline())
for _ in range(t):
n = int(stdin.readline())
used = [False for i in range(n)]
v = -1
for i in range(n):
l = [int(x) - 1 for x in stdin.readline().split()][1:]
for j in l:
if not used[j]:
used[j] = True
break
else:
v = i
if v == -1:
stdout.write("OPTIMAL\n")
else:
u = used.index(False)
stdout.write("IMPROVE\n" + s...
Educational Codeforces Round 84 Editorial, Разбор Educational Codeforces Round 84, n = int(input()) for i in range(1, n): res = 2 * 10 * 9 * p[n - i - 1] res +=
(n - 1 - i
168.
Educational Codeforces Round 66 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1175] [contest:1175] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-06-04] Glazov, Adilbek [user:adedalic,2019-06-04] Dalabaev, Vladimir [user:Vovuh,2019-06-04] Petrov, Ivan [user:Bl...
Educational Codeforces Round 66 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 66 (Rated for Div. 2)
169.
Educational Codeforces Round 141 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1783] [contest:1783] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-01-07] Dalabaev, Vladimir [user:vovuh,2023-01-07] Petrov, Ivan [user:BledDest,2023-01-07] Androsov, Ma...
Educational Codeforces Round 141 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 141 (Rated for Div. 2)
170.
Educational Codeforces Round 175 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/).
On [contest_time:2070] [contest:2070] will start.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2025-02-26] Dalabaev, Ivan [user:BledDest,2025-02-26] Androsov, Maksim [user:Neon,2025-02-26] Mescheryakov and...
Educational Codeforces Round 175 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 175 (Rated for Div. 2)
171.
Educational Codeforces Round 2 Привет, Codeforces!
[27 ноября 2015 года в 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+2&iso=20151127T1500) состоится второй учебный раунд Educational Codeforces Round 2 для участников из первого и второго дивизионов.
О формате и деталях проведения учебных раундов я писал уже [ранее](http://codeforces.me/blog/entry/21565). Также об учебных раундах вы можете прочитать [здесь](http://codeforces.me/blog/entry/21496).
Раунд будет нерейтинговым. Соревнование будет проводиться по немного расширенным правилам ACM ICPC. На решение задач у вас будет два часа. После окончания раунда будет период времени длительностью в один день в течении, которых вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования. Таким образом вы можете локально тестировать решение, которое хотите взломать, или, например, запустить стресс-тест.
Подготовкой ...
Educational Codeforces Round 2, /fixedtime.html?msg=Educational+Codeforces+Round+2&iso=20151127T1500) состоится
второй учебный раунд
Announcement of Educational Codeforces Round 2
172.
Educational Codeforces Round 138 Editorial [problem:1749A]
Idea: [user:BledDest,2022-10-21]
<spoiler summary="Tutorial">
[tutorial:1749A]
</spoiler>
<spoiler summary="Solution 1 (awoo)">
~~~~~
for _ in range(int(input())):
n, m = map(int, input().split())
for _ in range(m):
input()
print("NO" if n == m else "YES")
~~~~~
</spoiler>
<spoiler summary="Solution 2 (awoo)">
~~~~~
#include <bits/stdc++.h>
#define forn(i, n) for (int i = 0; i < int(n); i++)
using namespace std;
int main() {
int t;
scanf("%d", &t);
forn(_, t){
int n, m;
scanf("%d%d", &n, &m);
vector<pair<int, int>> a(m);
forn(i, m){
scanf("%d%d", &a[i].first, &a[i].second);
--a[i].first, --a[i].second;
}
bool ans = false;
forn(i, m) forn(x, n) forn(y, n) if ((x == a[i].first) ^ (y == a[i].second)){
bool ok = true;
forn(j, m) if (i != j){
ok &= x != a[j].first && y != ...
Educational Codeforces Round 138 Editorial, Разбор Educational Codeforces Round 138, Idea: [user:BledDest,2022-10-21] и [user:adedalic,2022-10-21], Идея: [user:BledDest,2022-10-21] и [user:adedalic,2022-10-21]
173.
Educational Codeforces Round 183 Editorial [problem:2145A]
Idea: [user:fcspartakm,2025-10-07]
<spoiler summary="Tutorial">
[tutorial:2145A]
</spoiler>
<spoiler summary="Solution (fcspartakm)">
~~~~~
#include <iostream>
using namespace std;
int main() {
int t;
cin >> t;
for(int i = 0; i < t; i++)
{
int n;
cin >> n;
cout << (3 - n % 3) % 3 << endl;
}
}
~~~~~
</spoiler>
[problem:2145B]
Idea: [user:BledDest,2025-10-07]
<spoiler summary="Tutorial">
[tutorial:2145B]
</spoiler>
<spoiler summary="Solution (Neon)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
int t;
cin >> t;
while (t--) {
int n, k;
string s;
cin >> n >> k >> s;
int a = count(s.begin(), s.end(), '0');
int b = count(s.begin(), s.end(), '1');
int c = count(s.begin(), s.end(), '2');
string ans(n, '+');
for (int i = 0; i < n; ++i) {
if (i < a + c || i >= n - b - c) ans[i] = '?';
if (i < a...
Educational Codeforces Round 183 Editorial, Разбор Educational Codeforces Round 183, Idea: [user:BledDest,2025-10-07], Idea: [user:adedalic,2025-10-07], Idea: [user:fcspartakm,2025-10-07], Идея: [user:BledDest,2025-10-07], Идея: [user:adedalic,2025-10-07], Идея: [user:fcspartakm,2025-10-07]
174.
Educational Codeforces Round 82 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1303] [contest:1303] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-02-11] Glazov, Adilbek [user:adedalic,2020-02-11] Dalabaev, Vladimir [user:Vovuh,2020-02-11] Petrov, Ivan [user:Bl...
Educational Codeforces Round 82 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 82 (Rated for Div. 2)
175.
Educational Codeforces Round 99 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1455] [contest:1455] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2020-11-29] Glazov, Adilbek [user:adedalic,2020-11-29] Dalabaev, Vladimir [user:vovuh,2020-11-29] Petrov, Ivan [us...
Educational Codeforces Round 99 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 99 (Rated for Div. 2)
176.
Eolymp Cup #1 
Eolymp Cup #1
=============
We are very excited to announce our new competition! Join us at [Eolymp Cup](https://basecamp.eolymp.com/en/contests/mufmafu7a932v5ofm9i93q65sc), a programming competition for students from everywhere! Take up a challenge to get a chance to win a trophy, medals, prizes, and scholarships at [Harbour.Space University](https://harbour.space/).
**Eolymp Cup** is a programming competition for students. The competition consists of 4 rounds, held throughout the year. Each round features 6 problems, each designed to challenge participants' knowledge of algorithms, data structures and programming.
The competition is open to everyone and will be held on [Saturday, July 6, 2024 at 17:00 UTC+2](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Eolymp+Cup%231+Round+1&iso=20240706T18&p1=367&ah=3). Still, prizes will only be awarded to participants who are currently enro...
each round, the top 10 institutions as well as 10 randomly selected
institutions among these who scored
177.
Educational Codeforces Round 176 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
The series of Educational Rounds continues thanks to the support of the [Neapolis University Pafos](https://www.nup.ac.cy/).
On [contest_time:2075] [contest:2075] will start.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2025-03-16] Dalabaev, Ivan [user:BledDest,2025-03-16] Androsov, Maksim [user:Neon,2025-03-16] Mescheryakov, Al...
Educational Codeforces Round 176 [Rated for Div. 2], ! The series of Educational Rounds continues thanks to the support of the
[Neapolis University Pafos, This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 176 (Rated for Div. 2)
178.
Hello 2025 by T-Generation Hello to all fans of competitive programming and Codeforces enjoyers! We're happy to invite you to participate in [contest:2057], which will take place on [contest_time:2057].
We, [user:teraqqq,2025-01-03], [user:dope,2025-01-03], and [user:induk_v_tsiane,2025-01-03], have prepared **8 problems** for you, and you’ll have **2 hours and 30 minutes** to solve them. One of the problems is divided into 2 subtasks. The round will be **rated** for all participants.
Huge thanks to [user:MikeMirzayanov,2025-01-03], [user:geranazavr555,2025-01-03], and [user:KAN,2025-01-03] for great systems Polygon and Codeforces!
Special thanks also go to:
- [user:FairyWinx,2025-01-03] for coordinating this round, finding testers, and providing moral and technical support.
- [user:turmax,2025-01-03], [user:LeoPro,2025-01-03], [user:Kapt,2025-01-03], [user:sevlll777,2025-01-03], [user:Pechalka,2025-01-03], [user:Adam_GS,2025-01-03], [user:evjeny_23,2025-01-03], [user:Iura_Shch,2025-01-03], [user...
into 2 subtasks. The round will be **rated** for all participants. Huge thanks
to
Announcement of Hello 2025
179.
Educational Codeforces Round 136 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1739] [contest:1739] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-09-28] Dalabaev, Vladimir [user:vovuh,2022-09-28] Petrov, Ivan [user:BledDest,2022-09-28] Androsov, Mak...
Educational Codeforces Round 136 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 136 (Rated for Div. 2)
180.
Codeforces Round #894 (Div.3) **☀ ☀ ☀ Hey Codeforces ☀ ☀ ☀**
----------------------------------
Summer is ending, but my team and I are happy to invite you to participate in [contest:1862]. The round will take place on [contest_time:1862]. You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of **open hacks**.
You will be given **7 problems** and **2 hours and 15 minutes** to solve them.
Note that the **penalty** for the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog/entry/59228) that only the trusted participants of the third division will be included in the official s...
Codeforces Round #894 (Div.3), the wrong submission in this round is **10 minutes**.
[Remember](https://codeforces.me/blog
Announcement of Codeforces Round 894 (Div. 3)
181.
Educational Codeforces Round 192 Editorial [problem:2242A]
Idea: [user:BledDest,2026-07-07]
<spoiler summary="Tutorial">
[tutorial:2242A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
k = int(input())
a = list(map(int, input().split()))
if max(a) > 2 or a.count(2) > 1:
print('YES')
else:
print('NO')
~~~~~
</spoiler>
[problem:2242B]
Idea: [user:FelixArg,2026-07-07]
<spoiler summary="Tutorial">
[tutorial:2242B]
</spoiler>
<spoiler summary="Solution (FelixArg)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
const int INF = 1'000'000'007;
void solve() {
int n;
cin >> n;
vector<int> a(n);
for (int i = 0; i < n; i++){
cin >> a[i];
}
vector<int> pref1(n + 1);
vector<int> pref2(n + 1);
for (int i = 0; i < n; i++){
pref1[i + 1] = pref1[i] + (a[i] == 1 ? 1 : -1);
pref2[i + 1] = pref2[i] + (a[i] == 3 ? -1 : 1);
}
int mn = INF;
for (int i = 1; i < n; i++){
...
Educational Codeforces Round 192 Editorial, Разбор Educational Codeforces Round 192, ] + (s[i] - '0')) % 10; for(int i = 0; i < m; i++) pt[i + 1] = (pt[i] + (t[i] -
'0
182.
Educational Codeforces Round 169 Editorial [problem:2004A]
Idea: [user:BledDest,2024-08-16]
<spoiler summary="Tutorial">
[tutorial:2004A]
</spoiler>
<spoiler summary="Solution (BledDest)">
~~~~~
t = int(input())
for i in range(t):
n = int(input())
x = list(map(int, input().split()))
if n > 2 or x[0] + 1 == x[-1]:
print('NO')
else:
print('YES')
~~~~~
</spoiler>
[problem:2004B]
Idea: [user:BledDest,2024-08-16]
<spoiler summary="Tutorial">
[tutorial:2004B]
</spoiler>
<spoiler summary="Solution (Neon)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
int t;
cin >> t;
while (t--) {
int l, r, L, R;
cin >> l >> r >> L >> R;
int inter = min(r, R) - max(l, L) + 1;
int ans = inter - 1;
if (inter <= 0) {
ans = 1;
} else {
ans += (l != L);
ans += (r != R);
}
cout << ans << '\n';
}
}
~~~~~
</spoiler>
[problem:2004C]
Idea: [user:BledDest,2024-08-16]
<spoile...
Educational Codeforces Round 169 Editorial, Разбор Educational Codeforces Round 169, const int D = 10; const int INF = 1e9;
183.
Educational Codeforces Round 60 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1117] [contest:1117] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.me/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Roms,2019-02-17] Glazov, Adilbek [user:adedalic,2019-02-17] Dalabaev, Vladimir [user:Vovuh,2019-02-17] Petrov, Ivan [user:B...
Educational Codeforces Round 60 [Rated for Div. 2], This round will be **rated for the participants with rating lower than 2100**.
It will be held on
Announcement of Educational Codeforces Round 60 (Rated for Div. 2)
184.
Educational Codeforces Round 156 Editorial [problem:1886A]
Idea: [user:fcspartakm,2023-10-10]
<spoiler summary="Tutorial">
[tutorial:1886A]
</spoiler>
<spoiler summary="Solution (fcspartakm)">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int n;
inline void read() {
cin >> n;
}
inline void solve() {
for (int x = 1; x <= 20; x++) {
for (int y = 1; y <= 20; y++) {
if (x + y >= n || x == y) continue;
int z = n - x - y;
if (z == x || z == y) continue;
if (x % 3 == 0 || y % 3 == 0 || z % 3 == 0) {
continue;
}
puts("YES");
cout << x << ' ' << y << ' ' << z << endl;
return;
}
}
puts("NO");
}
int main () {
int t;
cin >> t;
while (t--){
read();
solve();
}
}
~~~~~
</spoiler>
[problem:1886B]
Idea: [user:BledDest,2023-10-10]
<spoiler summary="Tutorial">
[tutorial:1886B]
</spoiler>
<spoiler summary="Solution (Neon)">
~~~~~
#include...
Educational Codeforces Round 156 Editorial, Разбор Educational Codeforces Round 156, Idea: [user:BledDest,2023-10-10], Idea: [user:Roms,2023-10-10], Idea: [user:fcspartakm,2023-10-10], Идея: [user:BledDest,2023-10-10], Идея: [user:Roms,2023-10-10], Идея: [user:fcspartakm,2023-10-10]
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