Hi, Codeforces!

I have some great news. But maybe you've already noticed? Seen the updated logo?

I'm glad to announce that Telegram is back as our title sponsor. I'm happy, and not just because this means we can keep developing and maintaining the system and (most importantly) running rounds for a long time to come.

But there's something else, too. It was Pavel Durov who, way back in 2010, spent several hours asking questions and trying to understand what I had in mind. Then he put his faith in our community — and Codeforces received support for the very first time. That support helped us for many years. So this means a lot to me personally, and I'm proud that now, more than 16 years after that first conversation, that support is coming back.

This helps with every round we run and gives us a chance to do new things, too. I'm glad to share that thanks to renewed support from Telegram, we've already started moving our infrastructure to a professional data center, making the system faster and more reliable.

I'm sure this won't be the only new thing happening soon. Expect more good news.

Mike

Hello, Codeforces!

I am very excited to invite you to participate in Codeforces Round 1122 (Div. 3), which will take place on Sep/21/2026 17:35 (Moscow time). You will be given $$$2$$$ hours and $$$30$$$ minutes to solve $$$7$$$ or $$$8$$$ problems. All problems were authored and prepared by me, WorldWarV.

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 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 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 rating of $$$1900$$$ or higher at any moment in time.

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 (unless you register unrated).

Also, note the rule restricting the use of AI. If you are caught breaking this rule, you will be dropped into cry's basement, which happens to be a permanently active volcano.

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

• cry for spectacular coordination of the round and answering all 998244352 of my questions;
• Edu175, __baozii__, Arpa for red testing;
• omsincoconut, CatsAreCool, Edeeva, Lilypad for orange testing;
• wakanda-forever, Argentum47, yse, SpyrosAliv, linearspace for purple testing;
• simplelife, Eikyu, nik_exists, silverkeep, expertaq, femboy for blue testing;
• ByteRaider for cyan testing;
• koseitsukamoto for green testing;
• Vladosiya for Russian translations and testing;
• MikeMirzayanov for developing Codeforces and Polygon.

GLHF!

Update: Editorial!

Hello, Codeforces!

We are excited to invite you to participate in Codeforces Round 1120 (Div. 1) and Codeforces Round 1120 (Div. 2) on Sep/12/2026 17:35 (Moscow time).

The round will be rated for participants from both divisions. You will be given 6 problems and 3 hours to solve them. At least one of the problems will be divided into subtasks.

The problems were authored and prepared by me, CutSandstone, and sukon.

We would like to thank:

• abc864197532 for being the coordinator.
• Um_nik for preliminary reviewing the round.
• Alexdat2000 for translating the statements to Russian.
• baluteshih, dlu, kevinyu, MattTheNub, n685, nadya271, yunz_qiao, _istil, alvingogo, avnithv, awoo, BurnedChicken, Fysty, Misuki, passwordisa, pbj2006, snowythecat, WiwiHo, and YuukiS for testing the round and providing valuable feedback.
• KAN and MikeMirzayanov for the great Codeforces and Polygon platforms.
• And finally,

  You

  , for participating!

The scoring distribution is:

1. Div. 1: $$$(500 + 1000)$$$ — $$$1750$$$ — $$$1750$$$ — $$$2500$$$ — $$$3000$$$ — $$$3250$$$
2. Div. 2: $$$500$$$ — $$$1000$$$ — $$$(750 + 1250)$$$ — $$$2250$$$ — $$$2250$$$ — $$$3000$$$

We hope you enjoy the problems.

Good luck and have fun!

UPD:

Congratulations to the winners (subject to change):

Div. 1:

1. Kevin114514
2. XorGhost
3. strapple
4. PiGoat
5. zjy2008

Div. 2 (trusted participants):

1. gausset
2. Dream_Sky
3. Guddu_06
4. Saransh_Gupta_
5. zhudaxia

UPD 2:

Sorry for the late tutorial, its posted now!

Привет, Codeforces!

Благодаря поддержке Neapolis University Pafos, продолжается серия образовательных раундов.

Во 08.09.2026 17:35 (Московское время) состоится Educational Codeforces Round 194 (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 решить 7 задач за 2 часа. Надеюсь, что каждый участник найдёт для себя интересные задачи в раунде.

Я бы хотел поблагодарить Михаила MikeMirzayanov Мирзаянова за создание платформ Codeforces и Polygon, которые сделали организацию соревнований и подготовку задач к ним очень удобным. Также большое спасибо тестерам: awoo, FelixArg, Alenochka.

Наши друзья из Neapolis University Pafos хотят поделиться с вами важной информацией:

Планируете поступление на программу Computer Science and Artificial Intelligence (CSAI) в Neapolis University Pafos?

Молодёжные клубы JetBrains помогут вам подготовиться.

🤖 AI Club — это возможность освоить одну из ключевых областей, которую вы будете изучать в рамках программы CSAI. Вы будете работать с темами, связанными с искусственным интеллектом, углублять свои знания и получать дополнительный опыт ещё до поступления в университет.

➗ Math Club поможет вам развить навыки математического решения задач, которые понадобятся вам во время обучения на программе. Кроме того, участие в Math Club даёт непосредственное преимущество при поступлении: участникам клуба может быть засчитано 30% от результата вступительного теста на программу бакалавриата Computer Science and Artificial Intelligence (BSc), существующую при поддерживаемую JetBrains Foundation.

Оба клуба предназначены для старшеклассников, которые интересуются STEM-дисциплинами, не боятся трудностей и готовы к следующему этапу своего образования.

👉 Присоединяйтесь к молодёжным клубам JetBrains: AI и Math

Успешных решений! Увидимся на раунде.

UPD: Разбор опубликован.

#include "codeforces.h"
#include <chrono>
#include <vector>

using namespace std;
using namespace std::chrono_literals;
using namespace cf;

int main() {
    Blog announcement("Codeforces Round 1119 (Div. 3)");

    announcement << "Hello Codeforces!\n";
    announcement << "I am delighted to invite you to participate in " << Codeforces Round 1119 (Div. 3) << "!\n";
    announcement << "The problems were written and prepared by " << nik_exists << ".\n\n";

    announcement << ContestInfo {
        .start_time = Sep/05/2026 17:45 (Moscow time),
        .duration = 2h + 15min,
        .number_of_problems = 7,
        .subtasks = true // possibly not adjacent
    };

    announcement << RatingRules {
        .rated_for_rating_below = 1600,
        .unrated_registration_allowed = true,
        .trusted_max_rating_below = 1900,
        .trusted_min_rated_rounds = 5
    };

    announcement << JudgingRules {
        .scoring = codeforces::ICPC,
        .wrong_answer_penalty = 10min,
        .open_hacking_phase = 12h,
        .final_tests = after_open_hacks
    };

    auto is_cheater = [](User user) {
        // https://codeforces.me/blog/entry/133941
        if (user.used_ai_in_contest()) return true;
        if (user.discussed_problems_online_before_contest_end()) return true;
        if (user.violated_other_rules_im_too_lazy_to_list()) return true;
        return false;
    };

    for (auto user : get_users(2259)) {
        if (is_cheater(user)) user.send_to_cry_basement();
    }

    announcement << Acknowledgments {
        .coordinator = cry,
        .russian_translation = Vladosiya,
        .red_testers = {__baozii__, AksLolCoding, awesomeguy856, nifeshe},
        .golden_testers = {Arpa, Intellegent, Proof_by_QED, temporary1},
        .purple_testers = {Argentum47, Euclid73, Jteh, Lilypad, SpyrosAliv, nimoxide, omsincoconut, wakanda-forever, yse},
        .blue_testers = {CatsAreCool, Vladosiya, chromate00, fatespeaker, linearspace, reirugan, simplelife},
        .green_testers = {hannah12345},
        .codeforces_and_polygon = {KAN, MikeMirzayanov}
    };

    announcement << "\nBest of luck, and thank y'all so much for competing!\n";
}

EDITORIAL

Приветствуем вас, фанаты олимпиадного программирования и любители написать раунды на Codeforces! У нас еще нет для вас раунда (это грустно), но зато есть кружок (это круто), где вы сможете обучиться новым алгоритмам, прорешать интересные задачи и многое другое!

Но даже без раунда перед постом хочется выразить благодарность MikeMirzayanov и команде Codeforces за замечательные системы Polygon и Codeforces! Благодаря этим системам, у нас есть возможность проводить кружок.

Т-Поколение "Алгоритмы и структуры данных" — это бесплатный кружок по подготовке к олимпиадам по информатике и спортивному программированию. Кружок проходит как онлайн, так и очно в Москве, Санкт-Петербурге, Нижнем Новгороде, Казани, Саратове, Ижевске, Перми, Уфе, Екатеринбурге, Челябинске, Томске, Новосибирске и даже в Минске. Учебная программа делится на 5 параллелей по уровню обучающихся:

• Параллель X предназначена для опытных олимпиадников, в ней преподают: Бабин teraqqq Александр, Нагибин Pechalka Всеволод, Белый antonis.white Антон.

• Параллель XS предназначена для тех, кто боится идти учиться в параллель X, но все равно хочет подготовиться к выступлению на финале ВсОШ. В этой параллели преподают: Грекова arbuzick Дарья, Белоусько Alcabel Константин, Валиуллин sadness Данис и Чистяков alexchist Александр.

• Параллель B предназначена для тех, кто уверенно проходит на региональный этап ВсОШ, хочет научиться проходить на заключительный этап и брать там диплом призера. В этой параллели преподают: Паншин doing Игорь, Сарапкин ArSarapkin Артем, Евстигнеев LargestNaturalNumber Георгий и Бессолицын BottleOfJuice Максим.

• Параллель B' предназначена для тех, кто на базовом уровне владеет C++, участвовал в муниципальных этапах ВсОШ и хочет подготовиться к региональному этапу ВсОШ и перечневым олимпиадам. В этой параллели преподают: Подворный Иван, Волков Smurf_with_me Алексей, Шейкис dope Марк и Хазеев ilgizarka Ильгизар.

• Параллель C предназначена для тех, кто на базовом уровне владеет Python или C++ и только начал свой путь в олимпиадном программировании. В этой параллели преподают: Ремпель DimaTomsk Дмитрий, Кривощеков robivirt Виктор, Антонова anadere Анна, Вашуркин Emvy Макар, Шатохин FedShat Фёдор и Чудинова Maria_Chudinova Мария.

Если вы готовы вкладывать свое время и старание в обучение, хотите взять всерос любой ценой, но бесплатно, то вам точно у нас понравится. Мы раздаем много мерча, преподаватели — опытные участники олимпиад высочайшего уровня, как в школьные, так и в студенческие годы, поэтому вам точно будет, чему у них научиться.

С правилами отбора вы можете ознакомиться по ссылке, 5 сентября, 16:00–21:00 по МСК будет очный отбор на все параллели. На него надо зарегистрироваться заранее и он будет проходить в очном+дистанционном формате тура на 5 часов.

Ссылка на отбор

Merhaba Codeforces!

We are proud to invite you to Codeforces Round 1118 (Div. 2), which will be held on Aug/29/2026 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 problems, one of which will be divided into a subtask, and 2 hours to solve them. Also, there is at least one interactive problem, so you are recommended to read the guide to interactive problems if you have not encountered them before.

The problems were authored by me (ItsNotMeItsYou), carcinisation, mychecksdead and Seferoglu.

This round was prepared by some members of the 2025 and 2026 IOI team of Türkiye, and we hope you enjoy all our problems.

We would like to thank:

• cadmiumky for his outstanding coordination of the round,

• Um_nik for the preliminary review,

• Alexdat2000 for Russian translations,

• MikeMirzayanov and KAN for Codeforces and Polygon,

• Our testers: destructive_criticism, tolbi, dinohaur, anpaio, kalimm, nifeshe, https, kafamcokkaristi, FatihCihan, LucaLucaM, PieArmy, int23_t, temporary1, robert9524, Kel_Mahmut, dead0ne, kawasaki, Synd209, elotelo, Anfeco,

• anpaio for improving at least one problem,

• destructive_criticism and dinohaur for at least one unused suggestion,

• You for participating in the round.

Score distribution: $$$500-(750+1000)-1250-2000-2250-3000$$$

Good luck & have fun!

UPD: The editorial is out! Sorry for underestimating the difficulties of the problems, especially B2 and D. We tried to serve as many cool problems as we could. And apparently, this led to some difficult ones.

Congratulations to the winners:

Official participants (subjects to change):

• xl123
• BTinn
• asterunee
• Alexander_0918
• no-girlfriend

Unofficial participants (subjects to change):

• xl123
• PiGoat
• BTinn
• maspy
• asterunee

Hello, Codeforces!

We are happy to invite you to an exciting online event: ICPC Online Challenge powered by Huawei.

This Challenge features the problem

Scheduling Algorithm for Collaborative Inference System With the rapid advancement of artificial intelligence, large language model (LLM) services are becoming increasingly integrated into people’s daily lives and work. At the same time, the economic efficiency and data security of these services are receiving greater attention.

Edge-Cloud Collaborative Inference has emerged as a promising approach to addressing these challenges. In this architecture, LLM inference is divided between a user’s on-premises edge environment and the cloud. Using a U-shaped split, the first and last layers of the model run on the edge, while the computationally intensive middle layers run in the cloud. This allows private inputs and outputs to remain on the user’s side while cloud resources are used for the heavier computation.

However, this architecture requires repeated interaction between the edge and the cloud during both the prefill and decoding stages. When requests are processed sequentially, these interactions can create “bubbles”—periods in which computing resources remain idle while waiting for other parts of the system.

Your challenge is to design a concurrent scheduling strategy that:

• maximizes overall system throughput; and
• ensures that every request satisfies its latency Service Level Objective (SLO).

Participants will need to carefully coordinate computation and communication across the edge and cloud while balancing throughput and per-request latency requirements.

We hope you will enjoy this challenging optimization problem inspired by real-world AI infrastructure.

Start: August 14, 2026 11:00 UTC (UTC+0)

Finish: August 28, 2026 10:59 UTC (UTC+0)

Prizes

By participating in this Challenge, you agree to the official Rules.

The use of AI tools, including generative AI and AI-assisted coding tools, is permitted during the Challenge. Participants remain fully responsible for the correctness, originality, and compliance of their submissions with all applicable rules.

To be eligible for a prize, you must register through: https://icpc.global/regionals/finder/ICPC-Online-Challenge-2026.

If you cannot access the rules document, please contact [email protected].

Good luck, and we hope you enjoy this complex yet exciting Challenge!

💻 Are you ready to test your problem-solving skills and push your limits in the world of algorithms and data processing? The Technology Olympics 2026 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): Friday, September 25, 2026
• Final Round (Onsite – Tehran, Iran): Wednesday, November 3, 2026
• Closing Ceremony: Thursday, November 4, 2026

The problems were authored and prepared by alireza_kaviani, mohammadsam, ArshiaDadras, AlefHeKaaf and AiPd.

📊 Data Processing Track

• Preliminary Round (Online – 24 Hours): Friday, September 11, 2026
• Final Round (Onsite – Tehran, Iran): Thursday, November 4, 2026
• Closing Ceremony: Thursday, November 4, 2026

🏆 Prizes for Each Track

Top 5 Teams in Preliminary Round:

• Travel support to Tehran (up to $200 per person)
• Hotel accommodation during the onsite final
• Meals and refreshments during the event
• Teams ranked 6th to 10th will also qualify for the onsite final

Cash prizes:

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

Cash prizes will be awarded upon participation in the onsite final. Qualified international teams will also receive travel and accommodation support according to the rules of each track, including:

• Travel support to Tehran (up to $200 per person)

• Hotel accommodation during the onsite final

• Meals and refreshments during the event

• Teams ranked 6th to 10th will also qualify for the onsite final.

• Qualified teams will be invited to an online briefing webinar before the final round, covering competition rules, travel arrangements, event schedules, submission procedures, evaluation criteria, and other logistical details.