Hello, Codeforces!

We are excited to invite you to DeepInfra Round 1 (Codeforces Round 1126, Div. 1 + Div. 2), which will take place on Oct/10/2026 18:05 (Moscow time)! Note the unusual start time of the round.

You will have 3 hours to solve 8 problems, one of which is divided into subtasks.

The problems were prepared by employed and reviewed carefully by nifeshe. We have put a lot of care into creating and testing this problemset, and we hope you will enjoy solving the problems as much as we enjoyed preparing them!

A huge thank you to everyone who helped bring this round to life:

• nifeshe for coordinating the round and being funny, cool, and smart!
• Dominater069 for the early review of the problems.
• EvenImage, AksLolCoding, ApraCadabra, Euclid73, linearspace, Mohammad_Hacker, naneosmic, nik_exists, omsincoconut, Pie_TealCompressorDragon, Rising-coder, Rvess, Sana, zyadhany, _______________________, FetFot, A_G, flammifer, and catgirl for testing the round and helping us improve the problemset.
• nifeshe for translating the statements into Russian.
• MikeMirzayanov and KAN for the Codeforces and Polygon platforms.

Honorable Mentions

A special thanks to our most disciplined testers, who joined the testing phase and successfully resisted the temptation to open a single problem:

cadmiumky, Um_nik, _istil, Intellegent, cgmoreda, sammyuri, Error_Yuan, cry, SpyrosAliv, and Arpa.

Thank you for your statistical contribution to the testing group's headcount.

Score distribution will be announced later.

And now, a few words from today's sponsor!

Hello Codeforces!

We’re excited to welcome you to DeepInfra Round 1

At DeepInfra, we build high-performance AI infrastructure that makes running the world’s best AI models fast, reliable, and accessible. We work across the entire inference stack—from GPUs to APIs—solving challenging engineering problems with a strong focus on performance and efficiency.

Our team has deep roots in Codeforces and competitive programming. One of us even competed in Codeforces Beta Round 50, so we’ve been around since the early days!

We prepared great prizes for the winners:

• Top 3: 1000 USDT + merch
• 4-6: 250 USDT + merch
• 7-10: 150 USDT + merch
• Random 10 from the top 100 (rank 11-100): merch

We’re growing! If you enjoy problem solving and want to work on challenging systems at the intersection of AI and infrastructure, we’d love to hear from you.

To apply for Software Engineering interns and full-time positions, fill in the application form and we will be in touch.

Good luck to everyone competing — have fun, and we’ll see you on the leaderboard!

— The DeepInfra Team

PS We reserve the right to apply strict compliance checks when finalizing the results in order to prevent unfair participation and rule violations.

Please note that prize delivery to certain countries, states, provinces, or territories may be subject to applicable sanctions, trade restrictions, or other legal requirements. We will make every reasonable effort to deliver prizes to all eligible winners, subject to any restrictions that may apply.

See you on the leaderboard. Good luck, have fun, and may your submissions turn green!

Hello Codeforces!

We’re excited to welcome you to the upcoming DeepInfra Round 1 🚀

At DeepInfra, we’re building high-performance AI infrastructure that makes running the world’s best AI models fast, reliable, and accessible. We operate across the entire inference stack — from GPUs all the way to the API — and we care deeply about performance, efficiency, and solving hard engineering problems.

Our team had great experience with being part of Codeforces and competitive programming community — PERNEKHAN, yessenzhar, Zharaskhan, Johan.de.Ruiter, rmn and many others. One of them even participated in Codeforces Beta Round 50 (so we're kinda OG here xD). That’s why we’re excited to be hosting this contest. We love meeting people who enjoy tackling challenging problems, thinking creatively, and pushing themselves technically.

We’re growing, too! DeepInfra is headquartered in Palo Alto, California, with an office in Sofia, Bulgaria, and we’re hiring software engineers and interns. If you enjoy this kind of problem solving and want to work on challenging systems at the intersection of AI and infrastructure, we’d love to hear from you.

To apply for Software Engineering interns and full-time positions, fill in the application form and we will be in touch.

Learn more about us and what we’re building on our website.

Join us on Oct/10/2026 18:05 (Moscow time) to win great prizes:

• Top 3: 1000 USDT + merch
• 4-6: 250 USDT + merch
• 7-10: 150 USDT + merch
• Random 10 from the top 100 (excluding top 10): merch

Good luck to everyone competing — have fun, and we’ll see you on the leaderboard! 🏆

— The DeepInfra Team

Hello! We invite you to participate in Codeforces Round 1125 (Div. 3), which will take place on Oct/07/2026 17:45 (Moscow time).

This will be a Division 3 round. You will be given 8 problems, authored by me and polished to perfection with the help of Noobish_Monk and Gornak40, as well as 2 hours and 30 minutes to solve them.

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.

We remind you that only trusted participants of the third division will be included in the official standings. This is a necessary measure to combat unsporting behavior. To qualify as a trusted participant of the third division, you must:

• have participated in at least five rated rounds (and solved at least one problem in each of them)

• have never had a rating of 1900 or higher.

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).

Note the rule restricting the use of AI. Previous announcements have already tried to scare you, so we will carry on the tradition: if you are caught breaking these rules, you will be sent straight into Gornak40's enclosure with the enraged gorillas.

I would like to thank the following people:

• Gornak40 for coordinating this wonderful round and destroying my long problem statements...

• Noobish_Monk for giving feedback on at least 50 problems before anyone else even got to see this round...

• Kapt, Ormlis for red-and-black testing of the round.

• KseniaShk, cry, snowysecret for yellow testing of the round.

• TheTitan008, Nogaybica, MrKisame for violet testing of the round.

• Mr.Backender, chromate00, OG_Maksimchick4, plushka_m for blue testing of the round.

• Kolyanchick, Everes, Dan1l0s, Hooded_Hood for cyan testing of the round.

• SqwoM, myav, naakinn, ChernovVladimir for green testing of the round.

• shishko.av, Margaryan_Armina for gray testing of the round.

• zetrock1 for unrated testing.

• Vladosiya for translating the problem statements into Russian wait, the statements were already in Russian. Thank you... for looking over the round and approving it for publication!

• MikeMirzayanov for Codeforces and Polygon.

Good luck!

Once upon a time, photos of the authors were a beloved tradition in Codeforces announcements — so we decided to take a little trip down memory lane.

upd: Congratulations to the winners!

Trusted participants:

1. phibrain
2. iaica1488
3. lixintianshen
4. JustPinkiePie
5. t3jtex

All participants:

1. abc864197532
2. paracompact
3. peti1234
4. leg
5. StarSilk

We have also published the editorial.

upd2: First solves by problems:

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!

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, Behrad., 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!

UPD1: The scoring distribution is released:

• Div. 1: $$$500 - 1000 - 1750 - 2250 - 2750 - 3250$$$;
• Div. 2: $$$500 - 1000 - 1500 - 2000 - 2750 - 3250$$$.

UPD2: Editorial

UPD3: Congratulations to the winners!

Div. 1

1. Ormlis

2. tourist

3. Elysion

4. jn_275

5. turmax

Div. 2

1. YerzhanU

2. -Fm2-

3. NiklasPlugin

4. zhude

5. kumod-Kumar

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

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!