Hello Codeforces!

mesanu, flamestorm and I are very excited to invite you to Codeforces Round 886 (Div. 4)! It starts on Jul/21/2023 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• 5-8 tasks;
• 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), then the round will be rated for you.

Many thanks to all testers: MikeMirzayanov, erekle, Bakry, Dominater069, Gheal, andrei_boaca, zwezdinv, sam571128, Sho, Wibo, Phantom_Performer, moonpie24, mafailure, Kalashnikov, SashaT9, Qualified, haochenkang, ZiadEl-Gafy, MADE_IN_HEAVEN, AdOjis485, qwexd, mkisic, Killever, sabbir-hasan-anik, peshkoff, donghoony!

And thanks to Vladosiya for translating the statements!

We suggest reading all of the problems and hope you will find them interesting!

Good Luck to everyone!

UPD: Editorial is out!

(っ▀¯▀)つ Heeey Codeforces (っ▀¯▀)つ

I and pavlekn are glad to invite everyone to participate in Codeforces Round 885 (Div. 2). The round will take place on Jul/16/2023 17:35 (Moscow time).

This round is dedicated to an amazingly beautiful girl Vika that I love very much. Every problem will be about her and related to her life.

The round will be rated for participants with rating lower than 2100. We will be glad to see the participants with a higher rating to take part in our round unofficially as well!

You will be given 6 problems to solve in 2 hours.

We would like to thank everyone that makes this round possible:

1. Artyom123 for coordinating the round

2. MikeMirzayanov for great Polygon and Codeforces platforms

3. teraqqq, Be_dos, mibig, FairyWinx, princebelkovetz for red testing

4. Dominater069, mbolgov, I.Gleb, induk_v_tsiane, Alexdat2000, maomao90, irkstepanov, fishy15 for yellow testing

5. Serik2003, alwyn for blue testing

6. TkachDan, ak2006 for cyan testing

7. maksimb2008 for grey testing

Scoring distribution: 500 — 1000 — 1500 — 2000 — 2250 — 2750.

We wish you all good luck and a high rating!

UPD: Editorial published

Hello, Codeforces!

I invite everyone to participate in Codeforces Round 884 (Div. 1 + Div. 2), which will start on Jul/11/2023 17:35 (Moscow time). The round is a combined round and will be rated for everyone.

You will be given 8 problems and 3 hours to solve them. One of the problems is divided into two subtasks. The scoring distribution will be:

$$$500$$$ — $$$1000$$$ — $$$1250$$$ — $$$1500$$$ — $$$2000$$$ — $$$(2000+1000)$$$ — $$$3500$$$ — $$$4000$$$

All problems are written and prepared by me. I would like to thank:

• irkstepanov for carefully coordinating the round.
• MikeMirzayanov for the wonderful Polygon and Codeforces platforms.
• 4fecta, ak2006, amethyst0, AndreySergunin, BalintR, ChrisT, Dan4Life, dorijanlendvaj, Dormi, errorgorn, Golovanov399, IndignantHydra, jonatas57, kzyKT, lexiyvv, liouzhou_101, Maksim1744, maximrufed, mc._cari, MvKaio, NoDesire, polosatic, RedstoneGamer22, skittles1412, tibinyte, valeriu for testing the round and providing valuable feedback.

I look forward to your participation and hope you enjoy the problems. Good luck!

UPD 1: Editorial

UPD 2: Congratulations to the winners!

1. cnnfls_csy
2. tourist
3. DearMargaret
4. ksun48
5. gyh20
6. heno239
7. jiangly
8. ecnerwala
9. neal
10. Sugar_fan

and congratulations to cnnfls_csy and orz for solving problem H!

Hello, Codeforces!

On Jul/07/2023 17:35 (Moscow time) Codeforces Round 883 (Div. 3) will start.

You will be offered 8 problems, dedicated to the adventures of a restless mathematician, a programmer and just a funny character named Rudolf, and 2 hours 15 minutes to solve them. Problems have expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

Note that the penalty for the wrong submission in this round is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. 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.

Problems have been created and written by: vladmart, Sasha0738 and natalina.

We would like to thank:

1. Vladosiya for coordinating the round.

2. MikeMirzayanov for Polygon and Codeforces platforms.

3. Sugar_fan for red testing.

4. 74TrAkToR, zwezdinv,Sokol080808,senjougaharin, FEDIKUS, Lucina, vrintle for yellow testing.

5. pavlekn, diskoteka, Phantom_Performer, bigDuck, Evirir for purple testing.

6. KoT_OsKaR, HappyChau0v0, bugdone, Termii, t0rtik, Rudro25, O_E, jhorvat, sohelH for blue testing.

7. ctraxxd, 666EGOR777, Guevara74, stefanbalaz2, jojonicho, hussein_auf for cyan testing.

Good luck!

UPD: Editorial is posted.

Hi Codeforces!

I welcome everyone to participate in Codeforces Round 882 (Div. 2) which will start on Jul/06/2023 17:35 (Moscow time).

The round will be rated for participants of Division 2 with a rating lower than 2100. I would encourage Division 1 participants to participate in the round unofficially.

You will be given 6 problems and 2 hours to solve them. One of the problem is interactive, so please read guide for interactive problems if you are not familiar with it.

All the problems are prepared by me and StArChAn.

We would like to thank:

• darkkcyan for going to Lebanon and doing Quality coordination.
• Alexdat2000 for translating problem statements.
• socho for helping with the initial stages of the round.
• astoria for giving problem idea of one of the problem and helping with the initial stages of the round.
• Spensa for grey testing.
• meghahegde for green testing.
• anuzrella, ak2006, ghosty, Trumling, Qualified for cyan testing.
• alwyn, nishuz for blue testing.
• Xc4l16r3, blue for purple testing.
• maomao90, vinfat, Mike4235, Dominater069, aryan12, 74TrAkToR, satyam343, AquaMoon for yellow testing.
• Umi, kshitij_sodani, Kuroni, thenymphsofdelphi for red testing.
• MikeMirzayanov for the great codeforces and polygon platform.
• You for participating in the round.
• Lastly, me for gong to Yemen and doing Treelike problem setting and writing this Thunderous blog.

Also, the editorial video for all the problems will be available on my channel right after the contest ends

All the best everyone!! Eager to see you going All Around The World and being Unstoppable in climbing the ranklist.

UPD: Scoring distribution — $$$500 - 1000 - 1500 - 2000 - 2750 - 3000.$$$

UPD: For video editorial of the problems, you can find it here

UPD: Editorial is out.

Hello Codeforces!

On Jun/29/2023 17:35 (Moscow time) Educational Codeforces Round 151 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

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 6 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

Intentionally Designed Solutions (IDS) has partnered with Harbour.Space University to offer Master’s degree scholarships to study Front-end Development, as well as work experience as a Front-end Engineer in a leading product development studio specializing in web-based solutions, including websites and web applications.

All successful applicants will be eligible for a 100% Tuition Fee Scholarship (29.900 €/year) provided by the Intentionally Designed Solutions (IDS).

CANDIDATE’S COMMITMENT

Study Commitment: 3 hours/day

You will complete 15 modules (each three weeks long) in one year. The daily class workload is 3 hours, plus homework to complete in your own time.

Work Commitment: 4+ hours/day

Immerse yourself in the professional world during your apprenticeship. You’ll learn from the best and get to apply your newly acquired knowledge in the field from day one.

RESPONSIBILITIES

• Collaborate with cross-functional teams to develop and implement innovative front-end solutions that align with project requirements and design specifications.
• Write clean, efficient, and maintainable code using modern front-end technologies, including Typescript and Svelte.
• Ensure seamless integration of front-end components with back-end systems, leveraging technologies such as MongoDB and Firebase.
• Demonstrate a basic understanding of smart contract technology, enabling the integration of wallets and blockchain functionality into web-based products.
• Lead and mentor junior developers, conducting code reviews and providing guidance to improve code quality and development practices.
• Drive the development arm of IDS's business by identifying opportunities to optimize processes, enhance efficiency, and improve overall team productivity.

REQUIREMENTS:

• Minimum of 2 years of professional experience in front-end development, with a focus on web-based products.
• Strong proficiency in Typescript and Svelte, with a solid understanding of front-end frameworks and libraries.
• Experience with back-end integration, particularly with MongoDB and Firebase.
• Basic understanding of smart contract technology and its application in web development.
• Previous experience managing and mentoring developers, conducting code reviews, and improving development processes.
• Excellent problem-solving, communication, and collaboration skills.
• Bachelor’s degree or equivalent experience.
• Advanced English level.

UPD: Editorial is out

Note the unusual start time of the round.

Hello, Codeforces!

Now that Gaokao is over, we are very glad to invite you to participate in CodeTON Round 5 (Div. 1 + Div. 2, Rated, Prizes!), which will start at Jun/24/2023 17:05 (Moscow time). You will be given 9 problems and 3 hours to solve them. The round will be rated for everyone.

All problems are written and prepared by Gary2005, Asuka, Crying, sjcsjcsjc, MonkeyKing, DerekFeng, KbltQaQ, ShmilyTY and me.

Statements and editorials will be available in Chinese (Simplified) after the contest.

We would like to give our sincere thanks to:

• errorgorn for his wonderful coordination!
• Alexdat2000 for translating problem statements.
• gyh20, wangziji, MagicalFlower, themoon, qiuzx, Atomic-Jellyfish, valeriu, nvmdava, mtw, AlperenT, ffao, AquaMoon, Umi, zengminghao, blobugh, Arraiter, FengzhuJian, He_Ren, LZDQ, CrTsIr, Pineapplello, feecle6418, 1.618, Alexdat2000, tzc_wk, WAtoAC2001 and tibinyte for testing this round and providing valuable feedbacks.
• MikeMirzayanov for the great codeforces and polygon platform.
• Lastly, we would like to express our gratitude to you for participating in the round.

The main character of the problems will be Tenzing Tsondu.

We hope that everyone can enjoy the round! As this round is sponsored, everyone will have an opportunity to win some prizes!

Good luck!

UPD1: Here is the score distribution:

250 — 500 — 1000 — 1500 — 2000 — 2500 — 3000 — 3750 — 5000

UPD2: Tutorial is available.

UPD3: Congratulations to the winners.

1. tourist
2. maroonrk
3. hos.lyric
4. cnnfls_csy
5. Um_nik
6. DearMargaret
7. jiangly
8. potato167
9. kotatsugame
10. noimi

UPD4: Congratulations to the first solver of each problem.

A: alexwice
B: ksun48
C: PinkieRabbit
D: Um_nik
E: Qingyu
F: amenotiomoi
G: tourist
H: rain_boy
I: maroonrk (after contest)

UPD5: Chinese statements

UPD6: Chinese editorials

Some information from our title sponsor:

Hello, Codeforces!

We, the Ton Foundation team, are pleased to support CodeTON Round 5.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 5 will receive valuable prizes.

The first 1,023 participants will receive prizes in TON cryptocurrency:

• 1st place: 1,024 TON
• 2–3 places: 512 TON each
• 4–7 places: 256 TON each
• 8–15 places: 128 TON each
• …
• 512–1,023 places: 2 TON each

We wish you good luck at CodeTON Round 5 and hope you enjoy the contest!

Hello, Codeforces!

On Jun/20/2023 17:35 (Moscow time) Codeforces Round 881 (Div. 3) will start.

You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

You will be given 7 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round is 10 minutes.

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.

Problems have been created and written by: zwezdinv, EJIC_B_KEDAX, molney, Sokol080808, meowcneil, Vladosiya.

We would like to thank:

1. Vladosiya for coordinating the round.

2. MikeMirzayanov for Polygon and Codeforces platforms and testing.

3. tute7627 for red-black testing.

4. ace5, sevlll777, oursaco, lightseba, gmusya, pavlekn, vrintle, tolbi for yellow testing.

5. diskoteka, moonpie24, SashaT9, shell_wataru, MGod, Phantom_Performer, tarattata1, alex.kudryashov, Restricted, sdyakonov for purple testing.

6. Alex239, MrEssiorx, olyazyryanova, marzipan, Pa_sha, Rudro25, azureglow, IHateGeometry, ivan.alexeev, krigare for blue testing.

7. Guevara74, ctraxxd for cyan testing.

8. sahal, exhausted, viteli, prohamer80 for green testing.

Good luck!

UPD: Editorial.

With a special dedication to all the people from Ukraine.

Hi, Codeforces!

I have the pleasure of inviting you to participate in Codeforces Round 880 (Div. 1) and Codeforces Round 880 (Div. 2), which will start on Jun/18/2023 17:35 (Moscow time). You will be given 6 problems and 2 hours to solve them in both divisions.

The problems were authored and prepared by Arti1990, Okrut, w0nsh, kempusss, Fly_37, kobor, maras, and me. As the tasks are based on problems from Polish Championship in Team Programming for High School, which takes place earlier on the same day, participants from the original competition are asked not to participate in this round nor share the problems.

I want to thank:

• 74TrAkToR for coordination, the round wouldn't be possible without him;
• Alexdat2000 for translating problem statements;
• jacynkaa, oogerbooger, Swistakk, natofp, GreatEagle, Grzmot, Maliniarz, viki88830, AlexLuchianov, Little09, Ecrade_, Kieray, pshat, piratZnachor, piegusek, E_huan, njupt_lyy, p_b_p_b, KeNaj712, Lavine, RUSH_D_CAT, and AquaMoon for testing and many, many advice how to make this round better;
• MikeMirzayanov for Codeforces and Polygon platform!

The scoring distribution:

Div. 1: $$$500$$$ — $$$1250$$$ — $$$1500$$$ — $$$1750$$$ — $$$2250$$$ — $$$3000$$$

Div. 2: $$$750$$$ — $$$1000$$$ — $$$1250$$$ — $$$2000$$$ — $$$2250$$$ — $$$2750$$$

Editorial

Have fun and good luck!