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 Sep/20/2025 17:35 (Moscow time) we will host Codeforces Global Round 29 (Div. 1 + Div. 2).

Codeforces Global Round 29 marks the first 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 problems were written and prepared by misteg168, FelixMP, Pablo-No, danx, MeGustaElArroz23, Clan328 and me.

We would also like to thank:

• Coordination: Um_nik

• 🍫 Nutella testing: gamegame, Ormlis

• 🍅 Tomato testing: ikaurov, prvocislo, NemanjaSo2005, Merkurev, tfg, TheScrasse and WLZ

• 🍌 Banana testing: rlidon2006, Esomer, Sergio_2357, KiKoS, Dalek_of_Rivia and -firefly-

• 🍆 Eggplant testing: JanBobi and rafatoa

• 🫐 Blueberry testing: AngrySeal, Lucia_Aparicio, chromate00 and eloipages

• 🥒 Cucumber testing: Kalufas

• 🥥 Coconut testing: dlos

• MikeMirzayanov and KAN for the great platforms

Round Information:

• Duration: 3h
• Number of problems: 9

UPD: Score distribution: $$$500 - 1000 - 1500 - 2000 - 2500 - 3000 - 4500 - 5500 - (4000 + 3500)$$$

UPD2: In this round, some of the problems will feature interactive visualizers that can help you to play around with small test cases. These are not part of the problem statements, although we tried our best to make sure that their behaviour correctly follows it. You can investigate examples or your own tests in more details with them. Note the following:

• the visualizers use javascript in your browser to work; you don't need to install anything additional;

• we won't be able to help with the visualizers during the round.

Picture of authors (and some testers) (and some non testers):

We eagerly anticipate your participation!

UPD3 Congratulations to all the winners!!!

1. ecnerwala
2. jiangly
3. ksun48
4. Benq
5. heuristica
6. turmax
7. strapple
8. Nachia
9. hos.lyric
10. Kevin114514

UPDT 4: Editorial is out: https://mirror.codeforces.com/blog/entry/146633

Hi, Codeforces!

Remember this post https://mirror.codeforces.com/blog/entry/105779 about highlighting test cases in example inputs?

Well, with a quick push, Vladosiya and I have now added support for highlighting cases in the outputs as well. On hover (or tap on mobile), the corresponding input and output cases even get highlighted together. Look at this beauty:

There's still a bit of polishing needed for situations when authors add custom outputs or in some other unusual scenarios, but the basic functionality is already there and ready to use.

Enjoy the upcoming rounds!

Hello, Codeforces! Or, as we like to say in Romania: Poți să îmi dai link la rundă în privat să testez?

We are proud to invite you to Codeforces Round 1051 (Div. 2), which will be held on Sep/17/2025 17:35 (Moscow time).

The round will be rated for participants whose rating is below 2100, but higher rated users are also welcome to participate out of competition. You will be given 6-7 problems, one of which will be divided into a subtask, and 2 hours to solve them.

The problems were authored by anpaio, tvladm, MateiKing80 and by yours truly.

We would like to thank:

• cadmiumky and Vladithur for coordinating the round,

• rolandpetrean waipoli Turcavid tibinyte2006 _istil Tudy006 mircea_007 madlogic Non-origination AlanSkarica ToniB andrei_C1 AleXutzZu __baozii__ cherryk -firefly- Andrei_ierdnA NemanjaSo2005 KALARRY chromate00 octa_bos A_G CatsAreCool Proof_by_QED khba InRainbows wuhudsm usuyus and welleyth for testing,

• Orzify for orzing the round,

• Alexdat2000 for Russian translations,

• MikeMirzayanov for Codeforces and Polygon,

• You for participating in the round.

Score distribution: $$$500 - 1000 - 1500 - (1750 + 1000) - 2500 - 3000$$$

Good luck & have fun!

UPD: Editorial is published: https://mirror.codeforces.com/blog/entry/146526

UPD2:

Congratulations to all the winners!!!

Div. 2

1. 72txdy
2. Terrorb1ade
3. bsmaN
4. guaidaokakaxi
5. FooFighter

Div. 1

1. ksun48
2. StarSilk
3. abc864197532
4. maspy
5. kotatsugame

Hi Codeforces,

Have you already spotted it in the schedule? Yes, the next Global Round is coming up on Sep/20/2025 17:35 (Moscow time)!

I'm excited to announce a series of three Global Rounds that we'll be holding in 2025. As always, these rounds are kindly supported by XTX Markets. Huge algorithmic thanks to them!

Each Global Round will be a common round for both divisions, featuring 7–9 problems. The contest length will be 2–3 hours, depending on the number and complexity of the problems. All rounds are rated for everyone. At each round, 50 branded T-shirts will be awarded, and of course, all problem authors will receive T-shirts too.

Prizes for this round:

• Top 30 participants will get a T-shirt.
• Another 20 T-shirts will be randomly given out among participants ranked from 31 to 500 (inclusive).

Prizes for the 3-round series in 2025:

• In each round, the top 100 participants will earn points according to the scoring table.
• A participant's final score will be the sum of points from their two best rounds.
• The top 20 overall will receive sweatshirts and certificates.

Wishing you a fun and memorable experience in the Global Rounds!

Привет, Codeforces!

Благодаря поддержке Neapolis University Pafos, продолжается серия образовательных раундов. Университет предлагает получение степени бакалавра в области компьютерных наук и искусственного интеллекта со стипендиями JetBrains. Получите передовые навыки в области искусственного интеллекта и машинного обучения, которые подготовят вас к востребованным техническим карьерам. Доступно ограниченное количество стипендий. Не упустите свой шанс учиться в Европе бесплатно!

В 15.09.2025 17:35 (Московское время) состоится Educational Codeforces Round 182 (Rated for Div. 2).

Этот раунд будет рейтинговым для участников с рейтингом менее 2100. Соревнование будет проводиться по немного расширенным правилам ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением, равен 10 минутам. После окончания раунда будет период времени длительностью в 12 часов, в течение которого вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования.

Вам будет предложено 6 или 7 задач на 2 часа. Мы надеемся, что вам они покажутся интересными.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Иван BledDest Андросов, Максим Neon Мещеряков и Роман Roms Глазов. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Удачи в раунде! Успешных решений!

Наши друзья из Neapolis University Pafos также хотят передать вам сообщение:

🚀 Бесплатные клубы по Математике, ИИ и Программированию
Университет Neapolis Pafos совместно с JetBrains приглашает школьников (13–19 лет) присоединиться к клубам по математике, искусственному интеллекту и программированию. Это еженедельные программы, созданные для прокачки ваших навыков решения задач через специально подобранные челленджи и живые сессии.

Не упусти шанс отточить свои навыки (и получить удовольствие от крутых миксов задач, которые подготовил pashka).

🔹 Математический клуб
Заложи прочный математический фундамент, чтобы улучшить свои навыки программирования. Каждую неделю ты будешь получать 10–15 постепенно усложняющихся задач, а также полуторачасовую живую сессию каждую субботу. Доступно два уровня сложности, так что ты можешь выбрать траекторию, которая тебе подходит.
💡 Лучшие участники получат 5 бонусных баллов на вступительном испытании на программу бакалавриата «Computer Science and Artificial Intelligence» в Neapolis University Pafos — это полностью финансируемая программа благодаря стипендиям JetBrains Foundation.
👉Присоединиться к Математическому клубу

🔹 Клуб Искусственного Интеллекта
Погрузись в мир искусственного интеллекта — от основ для начинающих до олимпиадных тем (например, IOAI). Присоединяйся к живым сессиям по средам и выполняй еженедельные домашние задания, чтобы постоянно прогрессировать.
👉Присоединиться к Клубу ИИ

🔹 Клуб Программирования
Идеальный вариант для тех, у кого уже есть опыт в спортивном программировании и кто хочет выйти на новый уровень. Каждую неделю — микс из задач с прошлых контестов Codeforces, который курирует Павел Маврин (чемпион мира ICPC 2004, серебряный медалист IOI 2002 и инструктор JetBrains Academy).
👉Присоединиться к Клубу Программирования

🎯 Продемонстрируй свои навыки:
Прими участие в третьем JetBrains Youth Coding Challenge — соревновании для школьников 13–19 лет. Лучшие участники будут приглашены на четвертый Algorithm and Code Training Camp (ACTS) 2026.1 в Румынии или на ACTS Online в январе 2026 года.

UPD: Разбор опубликован

I am extremely delighted to invite you to participate in my first solo round, Codeforces Round 1050 (Div. 4), starting on Sep/13/2025 17:35 (Moscow time). There will be $$$7$$$ problems to be solved in $$$2$$$ hours and $$$15$$$ minutes.

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 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), you may choose to participate rated or unrated.

PLEASE NOTE the rule restricting AI use. If you are caught using AI in an unorthodox manner, either by us manually or detected automatically, YOUR ACCOUNT WILL BE TERMINATED and your entire family will be sent to my basement (which has no toilets available). We will be actively scouring submissions and terminating rulebreakers.

I would like to thank the following individuals for making this contest possible:

• Myself for coordinating the round .

• Vladosiya for russian translations.

• reirugan for improving the statements.

• The following testuwuers: Proof_by_QED, reirugan, -firefly-, Filikec, Friedrich, mathtsai, __baozii__, Non-origination, chromate00, SpyrosAliv, Intellegent, Dominater069, Hori, RobinFromTheHood, pop, yse, Vladosiya, Lechaa, beaten_by_ai, macaquedev, catgirl, kingbass, tin.le2, ByteRaider, Trace_X1729, AksLolCoding, expertaq, kwant, santaclaus67, akane646, Hana05, .Habiba., apollo07, shuniko, Jteh, avighnakc, nifeshe, Edeeva, Eikyu, wuhudsm, and temporary1.

I know it has been a while without a division 4, so GLHF!

Editorial is Up!

Greetings Codeforces!

Ready to put your Kotlin skills to the test? Kotlin Heroes is your playground: a chance to experiment with the language's features, tackle fun and challenging problems, and level up your programming abilities. Perfect for beginners and experts alike!

A massive shout-out to all the amazing coders who have competed in past Kotlin Heroes events: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, Episode 8, Episode 9, Episode 10, Episode 11 and Episode 12.

Kotlin Heroes is a great way to play around with Kotlin’s features, learn something new, and practice using the language by solving fun problems. It is great for programmers of any level!

We invite you to join the practice round, where you can improve your algorithmic problem-solving skills and complete training problems. In this round, all the solutions are open, and you can request hints if you’re stuck.

Here are some things you can do to help you refresh your knowledge of Kotlin and learn more about competitive programming while you practice:

• Read our competitive programming tutorial.
• Review our Kotlin solutions for the Advent of Code algorithmic puzzles.
• Watch the videos from our Kotlin in Competitive Programming YouTube playlist.

And if you’d like to see how the top competitive programmers approach these challenges, check out ecnerwala and SecondThread solving problems from this practice round live on stage at the ICPC World Finals in Baku.

Mark your calendars for September 12, 2025! Kotlin Heroes: Episode 13 offers 2 hours and 30 minutes of problem-solving, featuring a wide range of tasks designed for everyone, from those just starting out to experienced competitive programmers.

The use of AI-based tools during the main contest is strictly limited. To find out the guidelines for proper AI use, what is allowed and what is prohibited, please read the post "Rule Restricting the use of AI". Improper use of AI tools during the main contest may result in disqualification. Using automatic translation tools (including but not limited to neural networks and AI) to convert code written in other programming languages to Kotlin goes against the spirit of the competition, so it is also strictly prohibited.

Prizes:

• 🥇 $512 (or equivalent value) for 1st place
• 🥈 $256 for 2nd place
• 🥉 $128 for 3rd place
• 👕 Kotlin Heroes T-shirts for the top 50 participants
• 🎁 A raffle of 50 T-shirts for anyone who solves at least one problem

Please note that we are not able to ship prizes to any country, state, province, or territory subject to comprehensive OFAC sanctions, including Belarus, Cuba, Iran, North Korea, Russia, Syria, or the Crimea, Donetsk, or Luhansk regions. For complete the list, please visit this page.

Best of luck to everyone!

upd: Editorial can be found here.

💻 Are you ready to test your problem-solving skills and push your limits in the world of algorithms and data processing? The Technology Olympics 2025 brings you two exciting competitions where creativity, logic, and technical mastery meet high-level challenges—and top teams win prizes!

🎈 Algorithm Track

• Preliminary Round (Online): Thursday, September 25, 2025
• Final Round (Onsite – Tehran, Iran): Thursday, October 30, 2025
• Closing Ceremony: Friday, October 31, 2025

📊 Data Processing Track

• Preliminary Round (Online – 24 Hours): September 26–27, 2025
• Final Round (Onsite – Tehran, Iran): Thursday, October 30, 2025
• Closing Ceremony: Friday, October 31, 2025

🏆 Prizes for Each Track

Top 5 Teams in Preliminary Round:

• Qualification for the Final Round
• Travel expenses up to $200 per person
• Hotel accommodation, local transportation, and meals in Tehran covered

Cash prizes:

• 🥇 1st: $600
• 🥈 2nd: $450
• 🥉 3rd: $300
• 🏅 4th: $250
• 🏅 5th: $200

Prizes for Teams Ranked 5th to 10th:

• Qualification for the onsite final round

Hotel accommodation, local transportation in Tehran, and meals have now been added to the prizes for the first-ranking participant from each country not in ranks 1–5!

Final Round: Total of $1,000 awarded to the top 3 teams!

Special Rule: At least one team from Iraq or Oman is guaranteed a spot in the Top 5.

Hello, Codeforces!

We are glad to invite you to participate in Codeforces Round 1049 (Div. 2) on Sep/09/2025 17:35 (Moscow time).

You will have $$$2$$$ hours to solve $$$6$$$ problems and some problems will be divided into subtasks. The round will be rated for participants whose rating is below 2100, but higher rated users are also welcome to participate out of competition.

The problems were authored and prepared by shorya1835, Divine_Spark and wakanda-forever.

We would like to thank:

• Sugar_fan for his great coordination.
• Alexdat2000 for Russian translation.
• doofushmirtz, Dragokj03, Shubham_KV and ho-oh, for proposing problems that later weren’t included in the final set.
• Our list of testers for providing valuable feedback: fallleaves01, _istil, Andreasyan, andrei_boaca, __baozii__, IceKnight1093, Tobo, Boboge, temporary1, ButterflyDew, BiggestOtaku, Proof_by_QED, Friedrich, Darko1, satyam343, Welcome24ever, madlogic, MaxBlazeIceInk, harshith_04, weirdflexbutok, milind0110, tridipta2806, chromate00, priyanshu.p and Non-origination.
• MikeMirzayanov and KAN for the great platforms.

Good luck & have fun!

UPD: Score distribution: $$$500$$$ – $$$1000$$$ – $$$1250$$$ – $$$1750$$$ – ($$$1750$$$ $$$+$$$ $$$1000$$$) – $$$2750$$$

UPD2: Editorial has been posted.

UPD3: Congratulations to the winners!

Div. 1:

1. arvindf232
2. cn449
3. kotatsugame
4. Rubikun
5. abc864197532

Div2:

1. Astitva_the_mahaan
2. ProfaSIO
3. RGB_ICPC8
4. Tenshi_
5. expi0i

Hello, Codeforces!

We are glad to invite you to participate in Codeforces Round 1048 (Div. 1) and Codeforces Round 1048 (Div. 2) on Sep/08/2025 17:35 (Moscow time).

The round will be rated for everyone. You will be given 6 problems and 3 hours to solve them in both divisions. Some problems will be divided into subtasks.

The problems were authored and prepared by installb, wjy666, tarjen, StarSilk and 2014CAIS01.

We would like to thank:

• maomao90 for his great coordination.
• Alexdat2000 for Russian translation.
• Um_nik, EvenImage and SSerxhs for red-black testing.
• A_G, -skyline- and __baozii__ for red testing.
• fishy15, oolimry, Boboge, Nanani, shstyle. and Tobo for orange testing.
• qsmcgogo and Retired_Zhisheng for purple testing.
• Husqqqq for blue testing.
• jellybean259 for green testing.
• akqxolotl for grey testing.
• MikeMirzayanov and KAN for the great platforms.

The scoring distribution is below.

• Div. 2: $$$ 500-1000-1500-2250-(2250+750)-3500 $$$
• Div. 1: $$$ 500-1250-(1250+750)-2500-(2750+1500)-4250 $$$

Good luck to everyone! (=^･ω･^=)

UPD：Unfortunately, it was discovered very lately (2 hours after the contest began) that the statement of div2D/div1B was missing an important condition. The correct statement should include the line "The operation 2 can only be applied at most once." The statement will be corrected soon.

We believe this issue affected many participants of this round, and therefore we have to declare this round unrated. We sincerely apologize for this mistake.

https://mirror.codeforces.com/blog/entry/146176 please refer to this blog for more information on why we decided to make the round unrated, and further elaborations on how this accident happened. We are deeply sorry for disappointing everyone, and we hope for your understanding.

UPD2: Here's the editorial: https://mirror.codeforces.com/blog/entry/146172