Καλησπέρα, Codeforces!

I am very excited to invite you to participate in Codeforces Round 1063 (Div. 2), which will take place on Nov/10/2025 18:05 (Moscow time). Please note the unusual starting time (30 minutes after the standard starting time).

You will be given 5 problems and 2 hours to solve them. At least one problem will be interactive, so please make sure to read the guide for interactive problems before the contest. This round will be rated for all participants with rating below 2100. The problems were authored by me, and prepared by Proof_by_QED and me. We are also excited to announce that:

This will be the first rated round to feature a communication problem.

Make sure that you are familiar with the problem format of communication problems. Recently, Testing Round 20 (Unrated, Communication Problems) was held in order to introduce this new type of problems. Please read the blog on communcation problems and familiarize yourself with these problems. Note that it is the first time we are experimenting with communication problems in a rated round, so please keep this in mind if you choose to participate.

Additional Note: In this round, hacks will be disabled on problems A,B,C and we will have pretests=systests. Hacks will be enabled on D,E as usual.

This round would not be possible without the help of the following people:

• Proof_by_QED for his very good (and first) coordination, and satyam343 for helping us both make this round better;
• Alexdat2000 for russian statement translation;
• The testers: Dominater069, A_G, Andreasyan, __baozii__, rui_er, _istil, nifeshe, Intellegent, fishy15, efishel, wuhudsm, AksLolCoding, FetFot, mzen, temporary1, turska, Timosh, cry, rangerscowboys, -firefly-, Friedrich, madlogic, pupilemus, sokratisi, pop, Lilypad, Edeeva, cowthecow, coder3000, macaquedev, Teto, chromate00, Non-origination, Stathis, pianapolataa, radaiosm7, beaten_by_ai, Vladosiya, Banis, AG-88301, Godgift42, streidi, ALnQ417, Ashrayy;
• MikeMirzayanov and KAN for Polygon and Codeforces platforms.

Score distribution: $$$500 - 1000 - 1250 - (1500 - 1250) - 2750$$$.

Editorial

Winners:

Div.1+2:

• jiangly
• maspy
• ksun48
• allvik66
• potato167

Div.2:

• KimikoLiliana
• duong3982
• Alex239
• chimbunhatvn
• Hello_zoka

Hello, Codeforces!

We are pleased to announce the resumption of the Global Rounds. Thanks to XTX Markets for supporting the initiative! In 2025, we will hold 3 such rounds. The series results will take into account the best 2 participations out of 3.

On Nov/06/2025 17:35 (Moscow time) we will host Codeforces Global Round 30 (Div. 1 + Div. 2).

Codeforces Global Round 30 marks the second round in the 2025 series of Codeforces Global Rounds. These rounds are open and rated for everyone.

The prizes for this round are as follows:

• The top 30 participants will receive a t-shirt.
• 20 t-shirts will be randomly distributed among participants ranked between 31 and 500, inclusive.

The prizes for the 3-round series in 2025:

• In each round, the top-100 participants get points according to the table.
• A participant's final score will be the sum of the points they earned in their 2 highest-placing rounds.
• The top 20 participants across the series will receive sweatshirts and placement certificates.

We extend our gratitude to XTX Markets for supporting the global rounds initiative in 2025!

The 8 problems were authored and prepared by our 8 authors: 244mhq, cmk666, Daniel777, JoesSR, Link_Cut_qwq, NetSpeed1, zjy2008 and me. There is at least one interactive problem, so I strongly urge you to read the guide if you are unfamiliar with the format.

We would also like to thank:

• 244mhq for his excellent coordination.
• Daniel081024, gyydp123_LIM, Little09, operator_, Zhouershan for discussing the tasks with us.
• Dominater069 and Um_nik for

  LGM

  testing.
• GroupMatrix, fake_banana, Imdie, zltzlt, _l_l_, _istil, hxhhxh, Daniel081024, nifeshe and omeganot for

  IGM

  and

  GM

  testing.
• awoo and qiuyuanzhi for

  IM

  and

  M

  testing.
• madlogic, hepp, Hori and Comentropy for

  CM

  testing.
• chromate00, Non-origination and larush for

  Expert

  testing.
• dazlersan1 for

  Specialist

  testing.
• _Jasonshan10_ and decimal10 for Unrated testing.
• 244mhq for translating the statements to Russian.
• MikeMirzayanov for creating the Codeforces and Polygon platform.
• And at last but not least,

  You

  for participating in the round!

Round Information:

• Duration: 180 minutes.
• Number of problems: 8 problems with 1 subtask.
• Score distribution: 500 + 750 + 1500 + 1750 + 2250 + (2500 + 1500) + 3500 + 5500

GL & HF!

UPD:

Congrats to the winners!

1. Otomachi_Una
2. Kevin114514
3. dXqwq
4. ksun48
5. VivaciousAubergine
6. qiuzx
7. strapple
8. hos.lyric
9. Radewoosh
10. StarSilk
11. tourist
12. maroonrk
13. potato167
14. Nachia
15. BurnedChicken

First Solves:

A: Away_in_the_heavens
B: ksun48
C: Depressed_sad_boy
D: ksun48
E: Kevin114514
F1: Otomachi_Una
F2: Otomachi_Una
G: qiuzx
H: rainboy

UPD2.

Editorial

Всем привет!

Мы обратили внимание, что уровень первой олимпиады оказался скорее средним, чем начальным, поэтому

• Вторая олимпиада будет проще первой и будет больше первой рассчитана на начинающих олимпиадников. Это не означает, что все задачи будут тривиальными, но для решения большинства из них будет достаточно знания базовых алгоритмов и структур данных.
• Третья олимпиада, как и планировалось, будет сложнее первой, и будет рассчитана на опытных участников.

Собственно, вторая интернет-олимпиада состоится в ближайшую субботу, 8 ноября 2025 года в 15:00 (по Московскому времени). Приглашаем вас принять в ней участие!

Продолжительность олимпиады – 5 часов, в течение которых вам будет предложено от 10 до 12 задач. Не забудьте зарегистрироваться на цикл командных интернет-олимпиад в этом сезоне перед началом олимпиады. Обратите внимание, что для участия в командных олимпиадах нужно зарегистрировать именно команду. Команда может содержать от 1 до 3 человек.

Ссылка на регистрацию команд доступна из данного анонса, а также на основном сайте интернет-олимпиад. Всю дополнительную информацию, а также расписание всех предстоящих командных интернет-олимпиад можно посмотреть на той же странице.

Условия появятся на сайте в момент начала олимпиады. Тестирующая система находится по адресу pcms.itmo.ru.

Олимпиаду для вас подготовили студенты/преподаватели Университета ИТМО: Павел Скобелин (pskobx), Даниил Орешников (doreshnikov), Егор Юлин (EgorUlin), Ильдар Гайнуллин (300iq), Антон Вдовин (AVdovin), Александр Гордеев (gordeve), Михаил Ермольев (ermolev04), Степан Мишанин (Mistep), Иван Пашков (Kisel001) и Олег Сметанкин (destrikes).

Для связи с жюри можно использовать адрес электронной почты [email protected].

Удачи!

UPD — разбор задач доступен на сайте интернет-олимпиад.

Hello Codeforces.

We are introducing a new type of problem which may appear in future Codeforces rounds, called Communication problems!

In these problems, your program would be ran twice, with different input and output formats between the runs. All variables stored in the memory will be lost between runs. However, the information given to you on the first run may be important to you for completing the second run correctly. Therefore, one of the key challenges in these types of problems would be to find a way to use the limited amount of output you are given in the first run to communicate information to the second run. Below shows a flowchart.

Flowchart for communication problems

In these problems, time and memory limits for both runs would be kept separately. For example, if a problem has a time limit of $$$2$$$ seconds, you will only get the Time Limit Exceeded if program runs for more than $$$2$$$ seconds on one of the runs, but not if both runs takes $$$1.5$$$ seconds.

It is also possible that a problem is both interactive and run-twice. There may be interaction on either run of your program. For these types of problems, it is especially important to read the problem statement carefully to ensure you are getting the input and interaction format correctly, especially regarding whether you must flush your outputs.

To give participants a feel of these new types of problems, we will hold Testing Round 20 (Unrated, Communication Problems), which will start on Nov/03/2025 17:35 (Moscow time). You will be given $$$1$$$ hour to solve $$$3$$$ run-twice problems. The problems are authored by cry, yse, SpyrosAliv, and chromate00. One problem on the set will be interactive, so you are recommended to read the guide for interactive problems if you are unfamiliar with these types of problems. Of course, this round will be unrated. Good luck, and I hope you will have fun with the new type of problem!

Edit: The contest will be in ICPC format with no pretests and hacks disabled.

Hey, Codeforces!** (*^‿^*)

Pinely is here! We are glad to invite you to participate in Pinely Round 5 (Div. 1 + Div. 2) which will start on which will start on 30.10.2025 19:35 (Московское время) Note the unusual time of the round.

• You will be given 8 problems and 3 hours to solve them. The round will be rated for everyone.

The problems were authored and prepared by pinely Endagorion ch_egor aleex AndreySergunin budalnik cdkrot gepardo gleb.shnshn Ormlis VArtem along with AmShZ and our special friend Golovanov399

Thanks for all your ideas, remarks, improvements and attention for details (*ˊᗜˋ*)/ᵗᑋᵃᐢᵏ ᵞᵒᵘ*

We would like to express our special thanks:

• Endagorion for curating the round on Pinely side and surviving through all storms

• errorgorn and KAN for the excellent coordination

• Testers team: Broder, jason_sun, efishel, A_G, CatsAreCool, reirugan, yuanruiqi, Wayne_Yan, madlogic, isaf27, weirdflexbutok, SirTechnical! (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧

• MikeMirzayanov for the great Codeforces and Polygon platform.

And, of course, you for participating (ᵔ◡ᵔ)

Prizes: The top 15 contestants will receive branded Pinely zip hoodies. Each hoodie can be personalized with custom name patches, making every prize truly unique.

To learn more about pinely you can visit our site or you can find our colleagues on CF in pinely organization.

UPD: Score Distribution

500 — 1000 — 1750 — 2250 — 3000 — 3250 — 3750 — 5000

☆ﾐ(o*･ω･)ﾉ Editorial is HERE

Congrats to winners! And everyone for participating ♥♥♥

• tourist
• Kevin114514
• Um_nik
• Petr
• jiangly
• Nachia
• ksun48
• hos.lyric
• BurnedChicken
• potato167
• VivaciousAubergine
• yosupo
• conqueror_of_tourist
• 353cerega
• 244mhq

Assalamu alaykum, Codeforces!

We are extremely excited to invite you to first-ever-Uzbek contest Codeforces Round 1062 (Div. 4), which starts on Oct/28/2025 17:35 (Moscow time). You will be given $$$7$$$ problems and $$$2$$$ hours and $$$15$$$ minutes to solve them. We hope you will find the problems interesting.

The problems were authored by khba, Muhammadali__, JahonaliX, Nasa and Isamatdin.

The format of the event will be identical to Div. 3 rounds:

• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behaviour. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

We would like to exceptionally thank:

• Vladosiya and soullless for wonderful and epic coordination.
• Kevin114514 for red-black testing.
• physics0523 for red testing.
• Friedrich, reirugan, Saturnalorbit, [VIP+] djm03178, [VIP] Intellegent, Odminbey, Arpa, catgirl, [VIP] Timosh and [VIP] cry for orange testing.
• [VIP] chromate00, khos, thismagic and M1LLI0N_PP for blue testing.
• MikeMirzayanov and KAN for the great platforms.
• and last but not least, You for participating!

Good luck to everyone and enjoy the problems!

UPD: Editorial is out

Всем привет!

Немного поздновато, но все же мы анонсируем второй тур цикла командных Интернет-олимпиад 2025-26.

Тур пройдет по задачам Ростовского регионального командного чемпионата школьников по программированию. Пожалуйста, обратите внимание: если вы уже зарегистрированы на тур в Ростове-на-Дону, вам необходимо участвовать в официальном туре. Интернет-олимпиада по тем же задачам – тренировочная, и не дает проход на ВКОШП!

Олимпиада пройдет уже завтра, 26 октября 2025 года в 13:00 (по Московскому времени), то есть на два часа позже старта официального тура. Приглашаем все команды, которые не принимают участие в официальном туре, принять участие в нашей олимпиаде :)

Продолжительность олимпиады – 5 часов. Не забудьте зарегистрироваться на цикл командных интернет-олимпиад в этом сезоне перед началом олимпиады. Обратите внимание, что для участия в командных олимпиадах нужно зарегистрировать именно команду. Команда может содержать от 1 до 3 человек.

Ссылка на регистрацию команд доступна из данного анонса, а также на основном сайте интернет-олимпиад. Всю дополнительную информацию, а также расписание всех предстоящих командных интернет-олимпиад можно посмотреть на той же странице.

Олимпиаду для вас подготовили: gifer, kkmstLeoni, AntonKozhevnikov, Ivan_Kislitsin, IvanovAlexandr и OrleanMagic.

Условия появятся на сайте в момент начала олимпиады. Тестирующая система находится по адресу pcms.itmo.ru.

Для связи с жюри можно использовать адрес электронной почты [email protected].

Удачи!

On the special day of 1024, I am very glad to invite you to participate in Codeforces Round 1061 (Div. 2), starting at Oct/24/2025 17:35 (Moscow time)

There will be six problems for you to solve in two hours, one of which will have two parts. At least one problem will be interactive, so please make sure to read the guide for interactive problem before the contest. This round will be rated for all participants with rating below 2100.

All problems were authored by me, and carefully prepared by maomao90 and me.

I would like to thank the following list of very strong individuals for making this round possible:

• maomao90 for his wonderful coordination and careful adjustments to some problems!
• MathModel for his excellent work on the editorial.
• Alexdat2000 for translating the statements into russian.
• Dominater069 and A_G for VIP testing
• Aging1986, __baozii__, PinkieRabbit, _istil, fishcathu, AC-Automation and Andreasyan for red testing.
• Darko1, K-423, -firefly-, mzen, newhar, Ye_Che, Leonard7 and wuhudsm for orange testing.
• DarkTemplarDrop, TosakaUCW, Siyah and huikang for purple testing.
• eleven-mile, the_only_noob, chromate00, MathModel, kreeeesh_17, Gingoo, cy171, arpit_kr, Leopold_Fitz for blue testing.
• jushuai_lfx and Route101 for cyan testing.
• 3alam, Aritro_, Gorko, _Robi, nlogn130, greenofyu for green testing.
• ItsAmirAli and M_902 for grey testing.
• MikeMirzayanov and KAN for the wonderful platform I have been with for 5 years.
• You, for participating.

Score distribution: $$$500 - 750 - 1500 - 2000 - 2750 - (3250 + 3250)$$$

Hope everyone will enjoy the round!

Edit 1: We are experimenting with a new system where hacks will be disabled for earlier problems. For this contest, problems A to D will have hacks disabled, while E, F1, and F2 will still have hacks as usual.

Edit 2: Editorial is posted.

Edit 3: Congratulations to the winners

Div1:

• ksun48

• TKT_YI

• peti1234

• maspy

• Sugar_fan

• potato167

Div2:

• DiegoGarcia

• donttalk

• 1225Xia

• RaresPoinaru

• zhoujingchen

• RaduM

I am very excited to invite you to participate in Codeforces Round 1060 (Div. 2), starting at Oct/19/2025 17:35 (Moscow time).

There will be 6 wowee problems for you to solve in 2 hours, some problems will have multiple parts. All problems were authored and prepared by me. This round will be rated for all participants with rating below 2100.

I would like to thank the following list of very strong individuals for making this round possible:

• satyam343 for epic coordination.
• Um_nik for preliminary review.
• The army of testers: Dominater069, sammyuri, __baozii__, Andreasyan, p0tato, _istil, nifeshe, anango, cry, wuhudsm, FetFot, [VIP] reirugan, turska, catgirl, https, That_Salamander, temporary1, -firefly-, [VIP] Proof_by_QED, [VIP+] Friedrich, efishel, Jasonwei08, Hori, Edeeva, welleyth, milind0110, kevlu8, Non-origination, lucaski2, vladimirfilip, dazlersan1, ALnQ417, eric899.
• myst-6 for being too enslaved to test.
• Alexdat2000 for translating the statements into russian.
• MikeMirzayanov and KAN for codeforces and polygon.
• You for participating.

Score distribution: $$$500 - 1000 - (1250 + 1000) - 1750 - 2500 - (2250 + 1750)$$$

UPD: Editorial

UPD2: Congratulations to the winners!

From Div. 2:

1. RGB_ICPC3

2. ljw01

3. paulo.pr

4. HusseinFarhat

5. happyhush

From Div. 1 + 2:

1. potato167

2. Geothermal

3. A_G

4. arvindf232

5. maspy

Hello, Codeforces!

I am very excited to invite you to our contest Codeforces Round 1059 (Div. 3), which starts on 17.10.2025 17:35 (Московское время). You will be given $$$2$$$ hours and $$$15$$$ minutes to solve $$$8$$$ problems.

The problems were authored and prepared by wakanda-forever, wuhudsm, tridipta2806 and frostcat.

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 before the contest.

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 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 that only the trusted participants of the third division will be included in the official standings table. As it is written by the link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them)
• do not have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

We would like to thank:

• cry for beautiful coordination.
• shorya1835, Divine_Spark and Krishbansal333 for proposing problems that later weren’t included in the final set.
• Dominater069 for LGM testing.
• __baozii__ for red testing.
• Friedrich, mayank69goel, shorya1835, aastik231205, reirugan, Intellegent, 18o3, Ming_Xu, Proof_by_QED, efishel and Arpa for orange testing.
• Edeeva, Prady, friedel, Forge, macaquedev, pop and omegaphi for purple testing.
• RustyGrill, Eikyu, HackerGupta069, DivinePunishment, Darsh_Jain, expertaq, Kushi, Krishbansal333, kingbass and chromate00 for blue testing.
• Trace_X1729, sanju77 and Maroon5_sugar for cyan testing.
• santaclaus67 for green testing.
• MikeMirzayanov and KAN for the great platforms.

I wish you the best of luck, and I hope you enjoy the problems!

UPD: Editorial