Xin chào Codeforces (・ω・)ﾉ

We are pleased to announce the resumption of the Global Rounds. Thanks to XTX Markets for supporting the initiative! In 2024, we will hold 4 such rounds. The series results will take into account the best 3 participations out of 4.

On Apr/06/2024 17:35 (Moscow time) we will host Codeforces Global Round 25.

Codeforces Global Round 25 marks the first round in the 2024 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 4-round series in 2024:

• 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 3 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 2024!

The problems were all marinated and cooked by MofK and Kuroni.

Our sincerest gratitudes go to:

• errorgorn for being the 🥶 and 😭 coordinator, and TheScrasse for being the 🧌 coordinator.
• xuanquang1999, gamegame, zeena., lanhf, Sana, TrungNotChung, lmqzzz, Umi, imsuck12, Saacoota, htetgm, kodomo_tachi, shine_, uocgimauxam, Pemguimn, Bananabread, hphuong, DeMen100ns, Kriz_Wu, milind0110, YangJackie, Vladithur, Ann, Endagorion, richzli, BucketPotato, and _FireGhost_ for testing and ensuring the balance of the round.
• Alexdat2000 for translating the statements to Russian.
• And of course, MikeMirzayanov for Codeforces and Polygon.

Round Information:

• Duration: $$$3$$$ hours.
• Number of problems: $$$9$$$ problems.
• Score distribution: $$$500 - 1000 - 1500 - 1750 - 2250 - 2750 - 3250 - 3500 - 4000$$$.

A tiny bit of personal note at the end, this is our first round on Codeforces in 3 years, and it feels a bit nostalgic to be back here again :) We eagerly anticipate your participation and let's all make it an awesome contest together!

UPD: Added score distribution.

UPD: The round has concluded. Congratulations to the winners!

1. Geothermal
2. ecnerwala
3. Um_nik
4. maroonrk
5. jqdai0815
6. Benq
7. hos.lyric
8. antontrygubO_o
9. cmll02
10. AlternatingCurrent

Tutorial can be found here, and playlist of songs used in the problem statements can be found here.

Привет, Codeforces!

Мы, AlperenT, flamestorm, ToxicPie9 и willy108, приглашаем всех на Codeforces на April Fools Day Contest 2024! 12-й Конкурс первоапрельских розыгрышей пройдет 01.04.2024 17:35 (Московское время). Это шутливое соревнование, в котором решение задачи часто проще, чем понять, что за задача вообще.

В этом раунде вам будет дано $$$n$$$ крутых багабу, где $$$-1 \le n \le \textbf{[REDACTED]}$$$, и 2 часа для их решения. В конкурсе будут использоваться расширенные правила ICPC (нет хаков, позиции определяются количеством решенных задач и штрафным временем, полученным за них). Вы можете отправлять решения на любом языке, разрешенном на Codeforces, если задача не указывает обратного.

Обратите внимание, что раунд не рейтинговый, и штраф за неправильное решение составляет 10 минут.

Чтобы представить, как будет выглядеть контест, вы можете посмотреть на контесты предыдущих лет: 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023. (Прошло 12 лет с первого Конкурса первоапрельских розыгрышей, спасибо Nickolas!)

Пожалуйста, не отправляйте никаких запросов на уточнение во время контеста, так как мы определенно не будем отправлять забавные ответы, как в прошлом году.

Удачи и веселитесь!

Hello Codeforcers!

We are pleased to invite you to participate in CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!). This round will start on Mar/30/2024 17:35 (Moscow time) and will be rated for all participants. There will be $$$8$$$ problems to be solved in $$$3$$$ hours, with one divided into two subtasks. Similar to USACO, you will help Farmer John and his cows resolve a series of first world problems. Be there or be square.

This round was cooked up by smax, sum, oursaco, cry, and buffering.

We would like to thank the following people for making the round possible:

• Our favorite cherry TheScrasse for the wonderful and speedy coordination.

• Our MVP testers, Benq, Geothermal, and rainboy, for dedicating so much time to reviewing problems, providing essential feedback, and perfecting the problemset.

• The rest of our testers for their unparalleled efforts: errorgorn, rqi, hyforces, LipArcanjo, MridulAhi, omeganot, darkkcyan, Phi-001, awesomeguy856, JagguBandar, camc, drdilyor, lethan3, rohit2593, willy108, WAtoAC2001, jay_jayjay, -1e11, evenvalue, lunchbox, kaztayev, kondasujay2, maxrgby, htetgm, thehunterjames, GlassesNerd, SunShine11, wozhenshuai, chromate00, I_FloPPed21, MrPavlito, priyanshu.p, ETL, yash_9a3b, Aurora__, nelsi_sousa, susvant, and myvaluska.

• Alexdat2000 for translating the statements to Russian.

• MikeMirzayanov for developing Codeforces and Polygon, or else this contest literally wouldn't exist.

• You, for participating!

Score Distribution:

$$$500 - 1000 - (1250 + 750) - 2250 - 2500 - 3000 - 3000 - 4500$$$

Editorial

Congratulations to our Winners and First Solves!

Top 5:

1. maroonrk

2. Radewoosh

3. ecnerwala

4. cnnfls_csy

5. orzdevinwang

First Solves:

A. A_G
B. jiangly
C1. ksun48
C2. turmax
D. Omer223
E. tourist
F. Radewoosh
G. tourist
H. ecnerwala

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 8.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 8 will receive valuable prizes.

The first 1,023 participants will receive prizes in TON cryptocurrency:

• 1st place: 1,024 TON
• 2–3 places: 512 TON each
• 4–7 places: 256 TON each
• 8–15 places: 128 TON each
• …
• 512–1,023 places: 2 TON each

We wish you good luck at CodeTON Round 8 and hope you enjoy the contest!

Hej, Codeforces!

mesanu, SlavicG and I are very excited to invite you to Codeforces Round 937 (Div. 4)! It starts on Mar/28/2024 17:45 (Moscow time).

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

• 5-8 tasks;
• 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 behavior. 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.

Thanks a lot to the testers: erekle, vladmart, nskybytskyi, Vladosiya, KrowSavcik, Dominater069, LucaLucaM, MADE_IN_HEAVEN, tvladm, nor.

We suggest reading all of the problems and hope you will find them interesting. Good luck!

UPD: The round is delayed by 10 minutes: https://codeforces.me/blog/entry/127616?#comment-1133556.

UPD: The editorial is posted!

Update: TON Tact Smart Challenge #2 has been postponed. More information here.

Please note: CodeTON Round 8 (Div. 1 + Div. 2, Rated, Prizes!) will take place as scheduled. We will be glad to see you among the participants!

Hello, Codeforces!

Have you heard about TON Tact Smart Challenge #2? It's an amazing competition organized by our title sponsor, the TON Foundation in their ecosystem.

This challenge is designed to engage participants in creating a decentralized social network prototype utilizing the Tact smart contract language. The project consists of five stages, each aimed at implementing a core feature of the social network, from user profiles to decentralized management.

We encourage the Codeforces community to participate in this contest. Dive deep into the world of TON Blockchain and explore the limits of what's possible.

Challenge starts on March 25, and lasts until April 3. To enter the challenge, register through @smartchallengebot. You'll receive all the essential details, including start times, submission guidelines, and insights into the challenge stages.

For more information, visit this page.

The scoring system is simple:

Each stage can bring you a max of 6 points. You get 5 points for solving a stage. You get an extra point if you solve it without using any gas.

Minimum amount of points to be eligible for the prize is 6 points.

Prizes:

• $7,000 in TON — The top 15% of eligible participants
• $7,000 in TON — The middle 30% of eligible participants
• $6,000 in TON — The bottom 55% of eligible participants

Impressive, right? Hurry up and join!

Good luck!

The European Championship 2024 will take place on the 24th of March in Prague. The top teams from the European ICPC regionals CERC, NWERC, SEERC, SWERC will compete for the title of European champions. It is the first edition of this ICPC super-regional.

The mirror contest European Championship 2024 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) will be held on Codeforces at Mar/24/2024 13:00 (Moscow time) and will last 5 hours.

The mirror contest will contain the same problems as the official competition.

I am the chief judge for the competition and I want to thank:

• The amazing set of judges who proposed and prepared the problems: antontrygubO_o, bicsi, Giove, Martin Kacer, MZuenni, Petr.
• Our beloved tester ksun48 who showed us that our perception of the difficulties was not exactly spot on...
• Our beloved proofreader Philae for proofreading the statements.
• Everyone involved in the organization of EUC. In particular our director Boba Mannová, and Fernando Silva, Václav Herman, Ondřej Votava, Jan Kubr, Jan Baier.
• The developers of DOMjudge, the contest system used in the official contest.
• MikeMirzayanov for Polygon (that we used to prepare the problems) and for letting us host the mirror on Codeforces.

I invite you to participate in the contest and I hope that you will like the problems.

On the difficulty
The contest features problems with difficulties from div1A to div1E. It should be enjoyable for many, and challenging even for the strongest teams in the world.

Rules

1. The contest is unrated, so your codeforces rating will not be affected.
2. The scoring is ICPC-style: teams are first sorted by number of problems solved, then the time-penalty is used as a tie-break. An incorrect submission gives a 20 minutes penalty.
3. We encourage participation as a team.
4. If you are participating in a team, we encourage you to use only one computer for coding the solutions (as in an ICPC contest). Regarding using templates, googling, and copy-pasting code: feel free to do it.

UPDATE: We hope you liked the problems!

Congratulations to the winners, and especially to the first two teams for AK:

1. dw my perception of the difficulties was not exactly spot on: tourist, ecnerwala.
2. xinyoudui: PubabaOnO, orzdevinwang, jqdai0815
3. MIPT: Yolki-palki: Tikhon228, Pechalka, Kapt
4. Captain take me!: crazy_sea, A_zjzj, 275307894a
5. Beyond Three Wolves: Kevin114514, CrTsIr, Atomic-Jellyfish
6. HSE: FFTilted: Kirill22, Ormlis

We uploaded the editorial of the contest.

Tune in to ICPCLive to see the closing ceremony and find out how the onsite teams did at 18:00 CET!

UPDATE 2:

Congratulations to the medalists of the onsite contest:

1. Warsaw Eagles 2024 — University of Warsaw (the only team with 9 problems)
2. Zagreb 1 — University of Zagreb
3. KNU_0_GB_RAM — Taras Shevchenko National University of Kyiv
4. ELTE 1 — Eötvös Loránd University
5. UWr 1 — University of Wroclaw
6. ENS Ulm 1 — École Normale Supérieure de Paris

Hola, Codeforces!

Мы рады пригласить вас принять участие в Codeforces Round 936 (Div. 2), который состоится в 22.03.2024 17:35 (Московское время).

Раунд был подготовлен exhausted, max0000561, azureglow и мной.

Этот раунд будет рейтинговым для участников, чей рейтинг ниже 2100. Участники с более высоким рейтингом могут принять участие вне конкурса.

Вам будет предложено 6 задач и 2 часа на их решение. Мы надеемся, что вам они покажутся интересными.

Мы хотим поблагодарить:

• 74TrAkToR за координацию раунда.
• Наших тестеров A_G, teraqqq, green_gold_dog, meowcneil, Noinoiio, sdyakonov, molney, IzhtskiyTimofey, zwezdinv, Nickir, Kihihihi, sergeev.PRO, lerasimus, 127.0.0.1, RomkaRS, makrav, Vash_nick, pskobx, VitalyKo, marzipan, zarubin, lunaTu, moniMono, xalwa, Gmix_Ivan_Zolo_57, Lelyte, KoT_OsKaR, __Foam, DamagedMoss5883, Iron_Fenix, OR_LOVe, Sonya_2009, tmari_sun, tfoppers, kuzyaa.
• MikeMirzayanov за платформы Codeforces и Polygon.

Отдельное спасибо хочется выделить KoT_OsKaR и teraqqq за помощь в создании задач.

Всем удачи на раунде и высокого рейтинга!

Разбалловка: 500−1000−1500−1750−2250−2750.

UPD: Дата проведения раунда изменена, чтобы избежать пересечение с соревнованием на другой платформе.

UPD: Разбор

UPD: We plan to host the 2024 Universal Cup Summer Summits in Cancún, Mexico. The event has been scheduled from June 19 to June 23. The detailed schedule, materials, and list of the invited teams will be announced in the future. The 2nd Universal Cup Semifinals will be held on June 23, 2024. The contest will start at 17:00 (UTC +8) and end at 22:00 (UTC +8). Please note that there will be no extra time windows on the semifinals contest — all the teams must start in the only official time window. You may check the event time on your local timezone here: Link. The onsite participants will participate in the semifinals on June 22nd (one day before the online participants)

Hello everyone, we are happy to announce the 2nd Universal Cup Semifinal and the 2024 Universal Cup Summer Summit.

In Season 2, thanks to everyone's support and efforts from our staff, there was a lot of progress compared to Season 1. We have over 3000 teams registered and so far we have scheduled over 30 stages in this season. We also managed to implement a registration webpage and host all kinds of contests on our platform, including the run-twice contest, the prime contest and the challenge contest. We also reached many agreements with Huawei about future cooperation, including the most exciting part: the onsite final. (Cooperation between Universal Cup and Huawei)

In the 2024 ICPC Latin American Championship, Universal Cup was invited to run the Huawei Challenge as a major part of the event. Our co-president Jingbang also gave a brief introduction of Universal Cup during the event to all the participants and coaches.

We still have more things coming! We have just finalized the rules for selecting the 2nd Universal Cup Final teams. The 2nd Universal Cup Semifinals will take place online, in order to select teams for the Final Contest. The contest is scheduled on one of the last two weekends of June (June 23 or 30). In addition, we have decided to host a special event, the 2024 Universal Cup Summer Summit in June. Supported by Huawei, we plan on inviting 10 teams to the wonderful city of Cancun, Mexico. The event will last around 5 days, including an onsite competition using the semi-final contest, a city tour, and some other activities. All fees will be covered by us. The exact schedule will be announced soon.

We want to express our gratitude again to everyone, especially problem-setters who have shared their wonderful contests with us. We are also planning to design souvenirs and prizes which will go to our contributors and participants, so stay tuned!

Here are the rules for the semifinal and the summer summit.

Universal Cup

2024.3.19

Обратите внимание на необычное время старта раунда.

Привет, Codeforces!

Во 19.03.2024 11:05 (Московское время) начнётся Codeforces Round 935 (Div. 3) — очередной Codeforces раунд для третьего дивизиона. 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-ти часовая фаза открытых взломов. Мы постарались сделать приличные тесты — так же как и вы, мы будем расстроены, если у многих будут падать решения после окончания контеста.

Вам будет предложено 8 задач и 2 часа 15 минут на их решение.

Штраф за неверную попытку в этом раунде 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 пяти 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.

Задачи основаны на олимпиаде ВКОШП.Junior. Авторы задач: Kirill_Maglysh, NToneE, Gadget.

Большое спасибо:

1. Vladosiya за прекрасную координацию раунда.

2. nigus, Gheal, KKT_89, Noinoiio, systy, FBI, SiERic, moonpie24, nik.danilov, SashaT9, Pa_sha, FedShat, an_na, khaser, Ghevar, Boris_Ber, PUFL, blook, yakuri354, iluminat_Btopou_AkkayHT за тестирование раунда.

3. gurovic за ценные комментарии по условиям задач.

4. MikeMirzayanov за системы Polygon и Codeforces.

Всем удачи!

UPD: Разбор выложен

Hello Codech....err i mean Codeforces!

I invite you to participate in Codeforces Round 934 (Div. 1) and Codeforces Round 934 (Div. 2) which will start on Mar/16/2024 17:35 (Moscow time).

You will be given 6 problems and 2 hours 15 minutes to solve them in both divisions. Division 1 has $$$\textbf{2 subtasks}$$$, and Division 2 has $$$\textbf{1 subtask}$$$.

Joining us on the problem setting panel are:

• Coordinator: Ashley errorgorn Khoo.

• Authors: Satyam satyam343 Kumar Roy, Aditya Everule Jain, Shreyan Dominater069 Ray.

• Russian Translation: Alexey Alexdat2000 Datskovskiy.

• Red Testers: Kostia kostia244 Savchuk, Jeroen jeroenodb Op De Beek, Andrei andrei_boaca Boaca, Luan LipArcanjo Arcanjo, Fernando ffao Fonseca, Alexander teraqqq Babin, Aleksei Vercingetorix Esin, Zixuan RDDCCD Yan, Aws Kaitokid Issa, hyforces.

• Yellow Testers: Naveen evenvalue Kulkarni, Kaio MvKaio Vieira, pavement, penguin133, zengminghao, Irmuun Irmuun.Ch Chinbat, Jared golions Goff, James jamessngg Sng, Sergey Kniaz Kniazevskiy, Chien-Yi -1e11 Chien, camc, Hriday the_hyp0cr1t3 G, Aryan aryan12 Maskara, Thomas oursaco, Weobe, Leonardo defnotmee Valente Nascimento.

• Purple Testers: Milind milind0110 Gupta, straw berr y.

• Blue Testers: Matthew chromate00 Roh, Ahmad Ahmad45123 Elwasefi, Kirill Sk0rlupka Kobets, Ivan peshkoff Peshkov, Yi Xiang Tyx2019 Tey, June cjc Chen, Kirill AbsurdMan Petrov, ExpensiveAC, Elyes ElyesChaabouni Chaabouni, Ianlsam, Non-origination, nsqrtlog

• Cyan Testers: Vyacheslav Kirito.LVL99 Komarov, Harsh Codula Sharma.

• Gray Testers: Sergey ansergeyg An.

• Negative Rated Testers: Cozma tibinyte Tiberiu-Stefan.

I would like to thank MikeMirzayanov for platforms Codeforces and Polygon.

Please do read a few problems in advance at the very least. Especially with all the subtasks, it is strictly in your benefit to read and choose the problems you want to try. Good luck. We hope you enjoy the problemset.

Score Distribution will be posted soon.

$$$\textbf{UPD}$$$ : Score Distribution :
Div2 : 500 + 1000 + 1500 + 2250 + 2250 + (2250 + 2750).
Div1 : 500 + 1250 + 1250 + (1250 + 2000) + (2000 + 1500) + 4500.

$$$\textbf{UPD2}$$$ : Sorry for the issue with the queue towards the end. Hope you enjoyed the round.

$$$\textbf{UPD3}$$$ :
Div2 :
1) WanYuanShenWanDe
2) tzc___________________wk
3) kcodex
4) mily
5) Oinng123

Div1 :
1) tourist
2) jiangly
3) gyh20
4) Benq
5) ecnerwala

$$$\textbf{UPD4}$$$ : Editorial is out.