Hello, Codeforces!

We are exited to invite you to participate in Codeforces Round 1124 (Div. 1) and Codeforces Round 1124 (Div. 2) which will be held on Sep/26/2026 17:35 (Moscow time).

The round will be rated for participants from both divisions. You will be given 2 hours and 30 minutes to solve 6 problems for each division.

The problems are authored and prepared by _R00T, eren__, sweetweasel, and me (Hamed_Ghaffari).

We would like to thank:

• Error_Yuan for coordinating the round.
• Um_nik for preliminary reviewing and testing the round.
• AmShZ, N_z__ for red testing.
• AKprinceofpersia, Arpa, Dindin, Mhn_Neek, misteg168, mohammadsam, msab3f, narges__ for orange testing.
• Behesht, Qazall, kian2009, rafieefatemeh for purple testing.
• SevenAlarm, Srsh, caibyte for blue testing.
• GUM for cyan testing.
• AlirezaBest for green testing.
• qhj0906 for gray testing.
• Alexdat2000 for Russian translation.
• MikeMirzayanov and KAN for the great platforms.
• You for participating!

The scoring distribution will be added soon.

We hope you enjoy the problems.

Good luck and have fun!

Hello, Codeforces!

We are glad and excited to invite you to take part in Codeforces Round 1123 (Div. 2), which will take place on Sep/25/2026 17:35 (Moscow time). You will be given 2 hours and 15 minutes to solve 7 problems. Problem F will be divided into subtasks.

Problems were authored by KluydQ, Aldk, YF_YUSUF, Dibamboo and Wansur.

We would like to give special thanks to:

• Um_nik for the preliminary review of this contest.
• 74TrAkToR for the great coordination and chance to host this contest.
• makrav, Kude, Friendiks, Error_Yuan, Sugar_fan, JovanB, lewc, Noobish_Monk, Daki-sa, ImDMka, Abilmansur-007, barbie, k1r1t0, Away_in_the_heavens, aryanc403, feresatcccccccc, Egorov_Dmitriy, QazLon, magagam, Arkanefury, Yessimkhan, liexes, GRIVA_, BzL16082010, spajzmand, knatwila, NickFuryy, PoDuReMaN, Dibamboo, AIibi for their time and effort in testing.
• MikeMirzayanov and KAN for the great Codeforces and Polygon platforms.

UPD: Editorial is available here https://codeforces.me/blog/entry/157126

Congratulations to the winners:

Div. 1:

1. StarSilk

2. __baozii__

3. solar_tree

4. maspy

5. Papaulo

Div. 2 (trusted participants):

1. solar_tree

2. jisoofan

3. kaiboy

4. GoogleBot

5. HADIA_ABD

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!

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos.

Educational Codeforces Round 194 (Rated for Div. 2) will start on Sep/08/2026 17:35 (Moscow time).

This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 7 problems and 2 hours to solve them. I hope everyone participating finds interesting problems for them to solve.

I would like to express my gratitude to Mike MikeMirzayanov Mirzayanov for creating Codeforces and Polygon, two platforms which made conducting programming contests and preparing problems for them much more convenient. Also big thanks to testers: awoo, FelixArg, Alenochka.

Our friends at Neapolis University Pafos have a message for you:

Planning to apply for the Computer Science and Artificial Intelligence (CSAI) program at Neapolis University Pafos?

JetBrains Youth Clubs can help you prepare.

🤖 AI Club is a chance to explore one of the core areas you’ll study in the CSAI program. You’ll work with AI topics, strengthen your understanding, and get more experience before university.

➗ Math Club helps you sharpen the mathematical problem-solving skills you’ll need for the program. There’s also a direct application benefit: participation in the Math Club can give you 30% of your entrance test mark for the Computer Science and Artificial Intelligence BSc supported by JetBrains Foundation.

Both clubs are designed for high school students with a strong interest in STEM who want to challenge themselves and prepare for the next step.

👉 Join JetBrains Youth Clubs: AI and Math

Good luck in solving the problems! See you at the contest.

UPD: The editorial has been published.

#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

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