Hello, Codeforces!

We gladly invite you to participate in Codeforces Round 1058 (Div. 1, Div. 2), which will be held on 12.10.2025 17:35 (Московское время)! You will be given $$$\mathbf{2.5}$$$ hours to solve $$$\mathbf{6}$$$ or $$$\mathbf{7}$$$ problems (depending on your division). One problem will be divided into two subtasks.

The problems were authored by wuhudsm, Proof_by_QED and chromate00. We have put so much effort (and time) into this contest, and we hope you will enjoy it!

Do note that for both divisions, at least one of the problems will be interactive. So if you are unfamiliar with them, please read the guide for interactive problems and get yourself ready.

Our team would like to thank the following people:

• TheScrasse for coordinating the round and believing in us for such a long time;
• Alexdat2000 for translating statements in this and every other contest;
• cry and sum for earning the "professional relaxer" title by not proposing problems;
• satyam343, BurnedChicken, zeemanz for VIP testing;
• Um_nik for shortly taking a look at the problemset;
• A_G, _istil, sammyuri, fextivity, cadmiumky, Dragos, IBory, szilb, awoo, rhombus, efishel, Intellegent, turska, adamant, beaaaan, spike1236, ArshiaDadras, qwexd, reirugan, rewhile, harshith_04, macaquedev, Edeeva, IvanBorquez, ProofByContradiction_, DivinePunishment, larush, tin.le2, ymwang, Non-origination, SpyrosAliv, and ALnQ417 for testing the problemset and helping us improve it;
• MikeMirzayanov and KAN for great platforms Codeforces and Polygon;
• and last but not least, You for participating!

And now, the score distribution.

Division 1:

Good luck, and I hope you find enlightment from the problemset!

UPD: Editorial is uploaded here.

Also UPD by chromate00: I sincerely apologize about the weak pretests of problem 1B/2E. I have greatly underestimated the runtime and memory usage of the worst solutions, while still wanting to be generous about slower solutions. This has led to weak tests during contest. Deeply sorry about the bad contest experiences affected by this.

Hello Codeforces,

We are very glad to invite you to participate in Codeforces Round 1057 (Div. 2), which will start on Oct/10/2025 17:35 (Moscow time). You will be given 6 problems and 2 hours to solve them.

All the problems are written and prepared by me and maomao90.

We would like to give our sincere thanks to:

• maomao90 for his wonderful coordination and careful adjustments to some problems!
• Alexdat2000 for translating problem statements.
• __baozii__, _istil, rui_er, AC-Automation, permutation, A_G, Andreasyan for red testing.
• -firefly-, K-423, frey4, Friedrich, Proof_by_QED for orange testing.
• xudian, Sofija06, qsmcgogo for purple testing.
• wink for blue testing.
• absi2011 for green testing.
• chou_maple for grey testing.
• MikeMirzayanov for the great codeforces and polygon platform.
• You for participating in the round.

The score distribution is $$$500 - 750 - 1250 - 1750 - 2250 - 3250$$$.

Hope everyone will enjoy the round!

Editorial is out now!

Hola, Codeforces!

We're glad to invite you to take part in Codeforces Round 1056 (Div. 2), which will start on Oct/05/2025 19:35 (Moscow time). You will be given 6 problems and 2 hours to solve them. At least one of the problems is interactive, so please read the guide for interactive problems if you are unfamiliar with them.

This round is based on the 30th edition of the Mexican Olympiad in Informatics (OMI).

Please note the unusual starting time.

The problems were authored and prepared by jampm, efishel, Marckess, JuanPabloAmezcua, IvanBorquez, SebR, Teto and me. We hope you enjoy the round as much as we enjoyed setting it!

The team would like to thank:

• errorgorn for his thoughtful coordination.

• Our legion of testers for their support and great feedback: Dominater069, Ari, _istil, prvocislo, nifeshe, 79brue, Intellegent, cry, Proof_by_QED, oursaco, osvarp, gxlois, prins, turska, racsosabe, Remgagagali727, _rey, prins, Bashca, JoenPoenMan, madlogic, Edeeva, Skywk, DonChipilin, CatsAreCool, chromate00, shucshin, AlexJzG, AlexRex0, Leonardo_Toral, Blagoj, _LeaRouse, Boas, pyedb48, beaten_by_ai, tjonac, Alexbrii, juanbrau.or, Baus, Ivanorey, EldoSantos, Rolexus, Jose_17, viktorchares, TonyRusher, Angel_liu, DEmmaRL, Juanchoki, Nitter, HatedFate, psr_codemaster21, JavierAriasHe, Daf-get34, RasecBadguy, Ansus11, Increedible

• Alexdat2000 for translating statements.

• KAN for believing in the project.

• ocarima, the godfather of the Mexican Olympiad in Informatics, for believing in us, all his support and pushing us to grow.

• MikeMirzayanov for creating codeforces and the amazing problem-setting system Polygon.

Score distribution: 500 — 1000 — 1750 — 2000 — 2250 — 3000

We wish you happy coding and good luck to all participants!

UPD 1: Added score distribution and new testers.

UPD 2: Added notice about interactive problems in the round.

Congratulations to the winners!

1. misty
2. Mirali777
3. BlackLily
4. AI-qv4rk
5. trigger.cpp
6. AKBEROV
7. dingdong
8. shade34
9. CAMOBAP31
10. aucoder123

UPD 3: Editorial is out! Sorry for the delay.

Annyeonghaseyo, Codeforces!

We invite you to participate in Squarepoint Challenge (Codeforces Round 1055, Div. 1 + Div. 2), which will be held on Oct/03/2025 17:35 (Moscow time).

The round will be rated for everyone. You will be given 8 problems, one of which is divided into two subtasks, and 3 hours to solve them. One of the problems will be interactive, so make sure to read the guide for interactive problems before the contest.

The problems are authored and prepared by middle_man, djm03178, ko_osaga, and qwerasdfzxcl.

We would like to thank:

• errorgorn for great coordination.
• Alexdat2000 for great Russian translation.
• Adam_GS, ainta, bangan, BuzzyBeez, cookiedoth, Dragos, gamegame, garam1732, Geothermal, gs20036, harshith_04, my_bloody_valentine, Shirakami_Fubuki, madlogic, badtreap, maomao90, mathjuny, MEDAAA, mujigae, nikolashami, Pacybwoah, PeruvianCartel, platter, rqi, Sana, sqwiijqk, Sugar_fan, tfg, ttamx, Waldi, we12223, wizardrabbit for great testing.
• MikeMirzayanov and KAN for the great platforms.
• You for participating!

As some of you may know, this contest originates from my promise to hold a Codeforces round if T1 wins a World Championship, which they did win afterwards in 2023 and 2024. This contest is dedicated to the T1 League of Legends team, and each problem will feature the members of their roster following the 2023 season. They are the sole reason for this project, so I want to extend my thanks to them and wish them the best of luck in their 2025 run! For those who are unfamiliar with the game, don't worry, as the problem statements are written neutrally anyway.

Score distribution is $$$500 + 1500 + 1500 + 2500 + 3000 + 4000 + 4000 + (4000 + 2500)$$$.

Now, a few words from our sponsor!

We are proud to support this competition and the talented participants who represent the future of our industry.

Squarepoint Capital is a global investment management firm with headquarters in New York City and London, and offices around the world. The firm is known for its quantitative finance approach to investing.

Igor Melnikov, Two-time winner of the All-Russian Mathematical Olympiad, First Prize at IMC in university, shares his insights on working at Squarepoint Capital:

"At Squarepoint, I'm surrounded by a team of exceptional individuals who share my passion for mathematics and competitive programming. As a winner of the National Olympiads in mathematics and an IMC medalist, I'm in good company — many of my colleagues have also participated in and won awards at national and international Olympiads. With a strong presence of Olympiad participants and medalists on our team, we bring a unique combination of mathematical rigor and problem-solving expertise to our work, and I'm excited to be a part of such a talented and driven team."

Squarepoint is actively hiring! If you have a background in engineering, computer science, mathematics, statistics, econometrics, financial engineering, operations research, or physics, and you’re proficient in at least one major programming or scripting language — this could be your opportunity.

🎁 Prizes:

• Top 5 performers will receive a $300 Amazon voucher each.
• Next 10 highest scorers will receive a $50 Amazon voucher each.

Good luck, and happy coding!

UPD: Thanks to everyone for participating! The editorial is here.

Top 15:

1. Nachia
2. qiuzx
3. BurnedChicken
4. Kevin114514
5. jiangly
6. tourist
7. strapple
8. ksun48
9. Um_nik
10. Otomachi_Una
11. VivaciousAubergine
12. Dominater069
13. ecnerwala
14. 7etuPr0mK_X-VPA.8-ER1SYJ
15. tiger2005

You might wonder: what kind of popular or controversial topic gets 175 comments?

The answer:

You are right! Codeforces edu section — Community Course! Most of the comments are "Still empty" :) But the good news is, this is not the case anymore!

I've just added the first set of tutorials on the RMQ Problem, which covers these three topics:

• Sparse Table
• SQRT Decomposition
• Disjoint Sparse Table

It's just a starting point, but hopefully, it will encourage others to contribute. Let's work together to build a high-quality collection of competitive programming materials! Check out a related comment below.

Let me know if you have any comments on the tutorials, which will help future writers as well.

Hello, Codeforces!

I am very excited to invite you to our contest Codeforces Round 1054 (Div. 3), which starts on . You will be given 7 problems and 2 hours and 15 minutes to solve them.

The problems were authored by me and __rose and soullless to solve and alter them.

The round will be hosted by the 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 — rank will be determined by number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of 10 minutes, following the rules of educational rounds.

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 point of 1900 or higher in the rating.

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.

We would like to thank:

• Vladosiya and soullless for wonderful coordination.

• Wansur and abc864197532 for red testing.

• ImDMka, Aldk and Away_in_the_heavens for orange testing.

• Hagry for purple testing

• Dif1rent, APMAH, sahaun and thespace for blue testing.

• 1BR444H1M, Batyi-A-019-28, HorridBear, Romakolesn and kartikchauhan189 for cyan testing.

• Erbolat-R-019-28, Yozhik and Fadlallah for green testing.

• MikeMirzayanov and KAN for the great platforms.

• Vinton Cerf, and Robert Kahn for inventing the internet.

• Nagi for not giving up football.

• You for participating!

UPD : the editorial is out.

Hello Codeforces!

Kotlin Heroes: Episode 13 brought together many talented participants, and we’re excited to share the results. Massive congratulations to the coders who tackled the challenges of Kotlin Heroes: Episode 13 and came out on top!

Top 3 contestants are:

1. tourist
2. Tlatoani
3. arvindf232

Kotlin Heroes T-shirts will go to the top 50 contestants:

These participants, who solved at least one problem, were randomly selected to receive special Kotlin Heroes T-shirts:

We’ll be in touch soon to coordinate prize delivery.

It's great to see new people learning Kotlin and performing brilliantly in the competition. Want to keep practicing? Challenges from all 13 previous rounds are available here: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round, Episode 6, Episode 7, Episode 8, Episode 9, Episode 10, Episode 11, Episode 12 and Episode 13.

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. If you’d like to sharpen your Kotlin skills, start with:

• Tour of Kotlin to learn the basics
• Algorithmic Challenges in Kotlin course, created by some of the competitive programming champions
• Competitive programming tutorial
• Videos on competitive programming in Kotlin from top competitive programmers

Good luck, and have fun with Kotlin! Until next time, heroes!

Ciao, Codeforces! We're glad to invite you to take part in Codeforces Round 1053 (Div. 1) and Codeforces Round 1053 (Div. 2), which will start on Sep/24/2025 14:35 (Moscow time). You will be given 7 problems and 3 hours to solve them in both divisions.

Note the unusual starting time.

• One of the problems will be divided into two subtasks.
• One of the problems will be interactive, so please read the guide for interactive problems if you are not familiar with it.

The problems were authored and prepared by Dominater069, satyam343 and me.

We would like to thank

• Dominater069 for his 😎 💀 😅 🙃 coordination;
• Alexdat2000 for Russian translation;
• Geothermal and jtnydv25 for VIP testing;
• isaf27, fextivity, maomao90, Adam_GS, A_G, SmolBrain, lethan3, IceKnight1093, cadmiumky, zeemanz, Sana, kshitij_sodani, Sugar_fan, Darren0724, guagua0407, efishel, satyam343, blue, CatsAreCool, chromate00, Non-origination for testing;
• MikeMirzayanov for creating Codeforces and Polygon.

Score distribution:

• Div. 1: $$$500 + 1000 + 1750 + 2500 + (2000 + 1750) + 3250 + 4250$$$
• Div. 2: $$$500 + 1250 + 1250 + 1750 + 2500 + 3250 + (2750 + 2500)$$$

We hope you'll like the problemset!

UPD: Congratulations to top $$$5$$$ in Div. 1 and Div. 2.

UPD 2: the editorial is out.