Hello, Codeforces!

I'm glad to invite you to Codeforces Round 732 (Div. 1) and Codeforces Round 732 (Div. 2), which will be held on Jul/11/2021 17:05 (Moscow time). Note the unusual start time of the round.

The round will be rated for both divisions. Each division will have 6 problems and 2.5 hours to solve them. There may or may not be an interactive problem, so I suggest you should read the guide for interactive problems.

All problems were written and prepared by CoupDeGrace, kuangbin, mejiamejia, Sugar_fan, Melacau, Nanako, GOATWU, Cirno_9baka, Suiseiseki, ODT, box, Ynoi, syh0313, wh0816 and me.

And thanks to QAQAutoMaton, gamegame, starusc, interestingLSY, chenkuowen, JianfengZhu, Monogon, ijxjdjd, Schwarzenegger, sunsiyu, Nezzar, bkbtpout, TheOneYouWant, gyz_gyz, kimoyami, njupt_lyy, ptd, coderz189, manik.jain, absi2011, gyh20, errorgorn, antontrygubO_o, oolimry, zhangzx123, wxhtzdy, tribute_to_Ukraine_2022, SonDinh, triple__a, Pecco, AzusaCat, dorijanlendvaj, Imakf, Falashiro, kartikeyasri23 for testing and good advice, isaf27 for his excellent round coordination and help with preparation and MikeMirzayanov for great systems Codeforces and Polygon.And you, for participating!

This is my first round ever. Great efforts have been put in during the past six months. We are sincerely looking forward to your participation. We hope everyone will enjoy it.

Good luck!

UPD1: Here's the score distribution:

Div 1: 500 — 1000 — 1500 — 2250 — (2000+2000) — 4000

Div 2: 500 — 1000 — 1250 — 1750 — 2250 — 3000

UPD2: Sorry to everyone! This is my first round and I spent lots of time to prepare it. I prepared at least 23 problems, and chose these eight ones for this round. I invited 35 testers to test, and chose problems according to their feedback. However, the difficulty is more than expect.And the pretest is not strong, leading to FST for many people. I blamed myself sadly. So I must say sorry to you, my dear friends. I will improve myself in the future. Wish you good luck and happy everyday. (๑•ᴗ•๑)

UPD3: Tutorial is available.

UPD4: Congratulations to the winners

Div1:

1.gisp_zjz

2.VivaciousAubergine

3.xtqqwq

4.Swistakk

5.Endagorion

Div2:

1.ki_msaga

2.jk-jung

3.RBurgundy

4.motomuman

5.flashsonic

Привет, Codeforces!

Мы, DK318 и unreal.eugene, недавно присоединились к команде разработчиков Codeforces и Polygon, в данный момент являемся студентами Университета ИТМО. Чтобы лучше ознакомиться с Polygon, мы участвовали в подготовке этого раунда. Совсем скоро вы сможете увидеть первые результаты нашей работы в качестве разработчкиков.

Кроме нас в разработке раунда принимали не меньшее участие MikeMirzayanov, geranazavr555 и doreshnikov. Надеемся, что вы получите удовольствие от решения задач!

В 10.07.2021 17:35 (Московское время) начнется Codeforces Round 731 (Div. 3) — очередной Codeforces раунд для третьего дивизиона. В этом раунде будет 7 задач. Задачи подобраны по сложности так, чтобы составить интересное соревнование для участников с рейтингами до 1600. Однако все желающие, чей рейтинг 1600 и выше, могут зарегистрироваться на раунд вне конкурса.

Раунд пройдет по правилам образовательных раундов. Таким образом, во время раунда задачи будут тестироваться на предварительных тестах, а после раунда будет 12-часовая фаза открытых взломов. Мы постарались сделать приличные тесты — так же как и вы будем расстроены, если у многих попадают решения после окончания контеста.

Вам будет предложено 7 задач и 2 часа 15 минут на их решение.

Штраф за неверную попытку в этом раунде (и последующих Div. 3 раундах) будет равняться 10 минутам.

Напоминаем, что в таблицу официальных результатов попадут только достоверные участники третьего дивизиона. Как написано по ссылке — это вынужденная мера для борьбы с неспортивным поведением. Для квалификации в качестве достоверного участника третьего дивизиона надо:

• принять участие не менее чем в двух рейтинговых раундах (и решить в каждом из них хотя бы одну задачу),
• не иметь в рейтинге точку 1900 или выше. Независимо от того, являетесь вы достоверными участниками третьего дивизиона или нет, если ваш рейтинг менее 1600, то раунд для вас будет рейтинговым.

Спасибо ashmelev, Monogon, CtrlAlt, Tzak, FelixArg, antontrygubO_o, bugdone и brian за помощь в тестировании раунда и улучшении задач.

Удачи!

UPD 1

Разбор задач.

Hello Codeforces!

I and DK318, as students of ITMO University, joined the Codeforces team in June. Last month we mainly dealt with the development of the Polygon platform and were focused on one significant feature lots of people dreamed of.

Have you ever made some changes to the problem, and at the same time another person changed the same file? I believe most of you did and disliked this situation. If you wanted to resolve the conflict, you needed to download an archive containing all your changes and repeat them all in the newest revision of the problem. This was very confusing and time-consuming, wasn't it? And now we present probably the most anticipated feature of Polygon since its creation: a web interface for resolving conflicts.

Hello Codeforces!

I am quite excited to invite you to my first ever round, Codeforces Round 730 (Div. 2) which will start on Jul/07/2021 17:35 (Moscow time). The round will be rated for participants of Division 2 (having rating strictly less than 2100). As always, Division 1 participants are welcome to participate in the round but it will be unrated for them.

The problems of this round will be themed on the 2005 video game Need For Speed: Most Wanted. You will be given 5 problems and 2 hours 15 minutes to solve them. One of the problems will be interactive. So, it is recommended to read the guide on interactive problems before the round.

I would like to thank -

• Aleks5d for coordinating the round and not rejecting any of my problems :)
• KAN for reviewing all the problems and providing invaluable suggestions throughout the round preparation.
• towrist and yash_daga for listening to my problem ideas even before I proposed them, providing invaluable suggestions and testing the round.
• Akulyat, andr0901, Mazaalai, talibmohd, nnv-nick, robert9524, DimmyT, kassutta, 4qqqq, wxhtzdy, karavaiev and asrinivasan007 for testing the round.
• amgfrthsp for translating the statements.
• MikeMirzayanov for the amazing Codeforces and Polygon platform.
• All the participants for participating.

I tried my best to create interesting problems with clear statements, strong pretests and useful sample test cases. Make sure to read all of them. Good Luck and Have Fun. See you on the Blacklist ranklist.

The score distribution is here: $$$500-750-1500-(1000+1250)-3000$$$.

UPD: Editorial

UPD: Congratulations to the winners

Div. 1 + Div. 2 -

1. Geothermal
2. Golovanov399
3. SSRS_
4. uwi
5. tfg

Div. 2 -

1. h0up1ngze
2. olmrgcsi
3. nicalvarez
4. LordVoIdebug
5. islingr

First Solves -

A: Geothermal
B: Geothermal
C: olmrgcsi
D1: h0up1ngze
D2: Golovanov399
E: tfg

Hello Codeforces!

feecIe6418 and I are glad to invite you to Codeforces Round 729 (Div. 2) which will start on Jul/03/2021 16:05 (Moscow time). Note the unusual start time of the round.

The contest will last for two hours, and you will have five tasks to solve. The tasks are prepared by feecIe6418 and me. This round is rated for participants whose rating is not higher than 2099.

We would like to thank:

• Aleks5d for coordinating and helping us with the problems.

• dorijanlendvaj, waaitg, Imakf, alexX512, Akulyat, talibmohd, Starlight-Sailor, andr0901, nnv-nick, Delmos, kassutta, wxhtzdy, 4qqqq, for testing the problems and providing useful feedback.

• amgfrthsp for translating the statement

• finally, MikeMirzayanov for great platforms Codeforces and Polygon!

It's the second time we hold our contest, our previous round Codeforces Round 670 (Div. 2).

We tried our best to make the statements short and clear, pretests strong and problems interesting. We hope you like the problems!

Score distribution will be announced shortly before the round.

Score distribution: 500-1250-1500-2000-(2000+1000)

Editorial is published Editorial

Congratulation to the winners:

Div1+Div2:

1.Nilou_

2.244mhq

3.jiangly

4.Benaive

5.Ormlis

Div2:

1.Nilou_

2.Benaive

3.hehezhouyyds

4.TuNormie04

5.SoilCrystal

Hello, Codeforces!

First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the five Kotlin Heroes competitions which were held previously: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, and Episode 6.

Ready to challenge yourself to do better? The Kotlin Heroes: Episode 7 competition will be hosted on the Codeforces platform on Jun/29/2021 17:35 (Moscow time). The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programmers.

Prizes:

Top three winners will get prizes of $512, $256, and $128 respectively, top 50 will win a Kotlin Heroes t-shirt and an exclusive Kotlin sticker, competitors solving at least one problem will enter into a draw for one of 50 Kotlin Heroes t-shirts.

Registration is already open and available via the link. It will be available until the end of the round.

The round will again be held in accordance with a set of slightly modified ICPC rules:

• The round is unrated.
• The contest will have 9 problems of various levels of complexity.
• You are only allowed to use Kotlin to solve these problems.
• Participants are ranked according to the number of correctly solved problems. Ties are resolved based on the lowest total penalty time for all problems, which is computed as follows. For each solved problem, a penalty is set to the submission time of that problem (the time since the start of the contest). An extra penalty of 10 minutes is added for each failed submission on solved problems (i. e., if you never solve the problem, you will not be penalized for trying that problem). If two participants solved the same number of problems and scored the same penalty, then those of them who had previously made the last successful submission will be given an advantage in the distribution of prizes and gifts.

If you are still new to Kotlin we have prepared a tutorial on competitive programming in Kotlin and Kotlin Heroes: Practice 7, where you can try to solve a few simple problems in Kotlin. The practice round is available by the link.

We wish you luck and hope you enjoy Kotlin.

Hello Codeforces!

ijxjdjd and I are pleased to invite you to participate in Codeforces Round 728 (Div. 1) and Codeforces Round 728 (Div. 2) which will be held on Jun/25/2021 18:35 (Moscow time). Please note the unusual timing. Each division will have 5 problems and 2 hours and 15 minutes to solve them.

We would like to thank:

• adedalic for amazing coordination of our round!

• singleLOOP, skittles1412, penguinhacker, wxhtzdy, coderz189, dorijanlendvaj, qlf9, Nezzar, Tlatoani, gotexans, Etherite, and prabowo for testing the round and providing invaluable feedback.

• MikeMirzayanov for the amazing platforms Codeforces and Polygon.

• You, for participating!

Read all of the statements carefully, and we hope you enjoy the problems! Wish you high ratings!

UPD: I would also like to thank Roberticey, malachi_toney_goat, and 244mhq for testing.

UPD: Here's the score distribution:

Div 1: 500 — 1250 — (1500 + 750) — 3000 — 3500

Div 2: 500 — 1000 — 1500 — 2250 — (2500 + 750)

UPD: The editorial is out!

UPD:

Congratulations to the winners!

Div. 1:

1. maroonrk
2. tourist
3. Radewoosh
4. LayCurse
5. NotaMotuaQAQ

Div. 2:

1. tampa
2. CF_is_my_GF
3. Apple_Method
4. rin-tohsaka
5. -this-is-obd-

Всем привет!

В воскресенье состоится всероссийская олимпиада школьников для 5-8 классов имени Келдыша. Удачи всем участникам! Олимпиада проходит под чутким руководством московской методической комиссии в лице GlebsHP, ch_egor, Endagorion, vintage_Vlad_Makeev, Zlobober, meshanya, cdkrot, voidmax, grphil и, конечно, Андреевой Елены Владимировны.

Мы рады представить Codeforces Round #727 на основе задач олимпиады. Это будет Div. 2 раунд, который состоится в 20.06.2021 13:05 (Московское время). Возможно, вы уже и раньше участвовали в раундах на основе олимпиад, подготовленных московской методической коммисией (раунды 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583, 594, 622, 626, 657, 680, 704, 707).

Задачи этой олимпиады были придуманы и подготовлены mutant, Siberian, shishyando, Artyom123, TeaTime, Tikhon228 под координацией grphil.

Также спасибо KAN, Aleks5d и isaf27 за помощь с организацией Codeforces версии соревнования и MikeMirzayanov за системы Codeforces и Polygon.

Также хотелось бы поблагодарить компанию Tinkoff и лично Татьяну TKolinkova Колинкову за неоценимый вклад в организацию соревнования.

Желаю удачи!

UPD1: Спасибо _overrated_ и Ormlis за тестирование.

UPD2: Разбалловка: 500 — 750 — 1250 — 1500 — 2000 — 2500

UPD3: Разбор

UPD4: Победители!

Div. 2:

1. Nilou_
2. newbiewzs
3. tou_xue
4. SoilCrystal
5. EEIEE

Div. 1 + Div. 2:

1. Maksim1744
2. kal013
3. jiangly
4. LayCurse
5. 2qbingxuan

Hello Codeforces!

mesanu and I are very glad to invite you to Codeforces Round 726 (Div. 2) which will take place on Jun/18/2021 17:35 (Moscow time). The round will be rated for participants with a rating lower than 2100. Division 1 participants are also welcomed to take part in the competition but it will be unrated for them.

The round was originally planned to be a division 3 round so the problems might be slightly easier than average Div 2.

You will be given 6 problems and 2 hours to solve them.

We would like to thank the following people:

• 1-gon for amazing coordination of our round!

• antontrygubO_o for testing, translating statements and providing useful ideas!

• Maksim1744, Ari, qpwoeirut, magnus.hegdahl, PurpleCrayon, Brodicico, Omkar, DenjellBoone, Arsenie, Lost_Arrow, Etherite, asrinivasan007, nishuz, cringeworthyplayz, Nika_Tamliani, Vpurice for testing and providing invaluable feedback!

• MikeMirzayanov for great Codeforces and Polygon platforms!

• You, for participating!

The scoring distribution is: 500 — 750 — 1000 — 1500 — (1250+1750) — 2000.

UPD: Editorial

Hello everybody!

After a long break I would like to announce the fourth Bioinformatics contest organized by ITMO University, Bioinformatics Institute, Rosalind and Stepik. The contest is sponsored by JetBrains, Yandex, Serokell, and Genotek.

The contest is hosted on Stepik platform. To participate you have to sign the rules.

The contest consists of two rounds:

• The Qualification round is already started today. It will be open until June 19 11:59 UTC+0.
• The Final round will be held for 24 hours starting at June 26 13:00 UTC+0.

The contest is prepared by the following team: Alexey Sergushichev, Nikita Alexeev, budalnik, demon1999, tourist, cdkrot, GShark, doreshnikov (all ITMO University), German Demidov (Center for Genomic Regulation), Andrey Prjibelski (CAB SPbU).

Are there any prizes?

• 1st place – Whole Genome Sequencing
• 2nd and 3rd – Whole Exome Sequencing
• 4th and 5th – 23andMe or Genotek DNA Service
• 1st–30th – Honorable Bioinformatics T-Shirt

Do I need to know biology?

The knowledge of biology is not necessary to solve the problems!

We wish that you will like the problems!

Good luck!