Hello, Codeforces!

We are pleased to invite you to Pinely Round 4 (Div. 1 + Div. 2), which will start on Jul/28/2024 17:35 (Moscow time). The round will be rated for everyone.

You will be given 9 problems and 3 hours to solve them. There is at least one interactive problem, so please read the guide for interactive problems if you are unfamiliar with it.

The problems were authored and prepared by me.

We would like to thank:

• errorgorn for the excellent coordination.
• dXqwq, StarSilk, jiangbowen_, Endagorion, JCY_, jiangbowen, QwertyPi, chen_zexing, YocyCraft, zeliboba, HackerMonk, axs7384, Vladithur, davi_bart, prvocislo, leinad2, Andyvanh1, stasio6, hychyc, bitset, bonopo, Mucosolvan, RandomLB, CSQ31, Myrcella, NamelessOIer, guapisolo, Enigmurl, satyam343, Vingying0, qinyuzhou, 7oSkaaa, Geisel.Library, EpicChadGamer, AXXWTGST, and pengrui for testing the round and providing valuable feedback.
• Alexdat2000 for translating the statements to Russian.
• MikeMirzayanov for the great Codeforces and Polygon platform.

We hope you will enjoy the round!

Score distribution: $$$250 - 500 - 1000 - 1500 - 2000 - 2500 - 3000 - 3500 - 4000$$$

The editorial is here.

Congratulations to the winners!

1. tourist
2. jqdai0815
3. Radewoosh
4. ksun48
5. Rewinding
6. hos.lyric
7. jiangly
8. Benq
9. BurnedChicken
10. Szoboszlai10

This round is made possible with the support of Pinely!

Pinely is a dynamic algorithmic trading firm with a presence in Singapore, the Netherlands, and Cyprus. We specialize in high-frequency and ultra-low latency trading. Our team of mathematicians, programmers, engineers, and computer scientists tackles everyday challenges like developing trading strategies, optimizing systems for minimal latency, saving and processing large volumes of historical data.

Working at Pinely demands exceptional C++ coding, algorithmic thinking, and mathematical intuition, attracting top talent, including winners and awardees of such competitions as ICPC, IMC, HITB PRO CTF, Google HashCode, etc.

Learn more about us on our website or find our employees on CF. To join our team, please send your CV to [email protected], even if you are not participating in the contest.

Prizes: The top 30 contestants will receive a branded plush pine tree!

Hewwo Cowodeforcers!

sum and I are overjoyed to welcome you to participate in Codeforces Round 962 (Div. 3) on Jul/26/2024 17:35 (Moscow time). This contest is the last stop on our mission to problemset for every division. We hope you've been enjoying our stuff so far!

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. After open hacks all accepted solutions will be rejudged on successful hacks.

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

Note that the penalty for each 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.

We would like to orz the following individuals for making the contest possible:

• Vladosiya for the quality coordination.

• Benq and satyam343 for overseeing the creation of this contest.

• Yam, omeganot, tyr0Whiz, awesomeguy856, 18o3, Sokol080808, Phi-001, milind0110, NovusStellachan, vgoofficial, carnation13, SashaT9, Pa_sha, Qualified, Prady, ntarsis30, waidenf, Non-origination, Orange905, AceKnight7, ETL for testing the contest and providing valuable feedback.

Thank you for reading and we hope you have a fun and educational interstellar adventure :3

UPD: Editorial

Attention! Attention! Attention! Don't miss this opportunity!

Codeforces Round 961 (Div. 2) will be held on Jul/23/2024 17:35 (Moscow time)!

Problems for this round were prepared by a team of Neapolis University Pafos (yes, you've seen its logo in Educational Round announcements) students: Vitaly503, goncharovmike, ikrpprppp.

You will be given 5 problems some of which will be divided into two subtasks and 2 hours to solve them.

Important disclaimer! Some problems of this round were also used in CPFED x JetBrains Training Camp 2024. NUP Contest in Kazakhstan this June. If you've participated in this camp or seen the problems from there, please do not participate in this round.

We would like to thank:

• Akulyat for coordinating the round and frequent pinging;

• pashka for valuable discussions and the idea of one of the problems;

• MikeMirzayanov for the all-powerful Codeforces and Polygon platforms;

• Our testers denk, artem3605, physics0523, BurnedChicken, oursaco, AdityaTakkar, shade34, md_nihal, Vamperox, Binary_Thinker, Dominater069, -2.71, Yugandhar_Master, Banis, dazlersan1, MaxLevitsky, larush, aufannn, thenymphsofdelphi, turmax, ishaandas1, vahtang, GrandFruit, okwedook, Vladithur;

• Participants of the onsite version of this contest in Kazakhstan who also made this round better: AmirMakaM, kaztayev, MnTm, shenfe1, mispertion20, dondurma, N29, Relice, k1ngash, Alihan_8, Otalp, Tima19, kanye_east, adiyer, BallBreaker, I_Love_Diar_Narumov, Tangirkul, Issa, fft97, Aiperiii, Bichpaket, Baytoro, kylych03, Wansur, Chalishkan;

• And participants of the Codeforces Round 961 (Div. 2) (i.e. you)!

Not-so-important not-so-disclaimer. If you're interested in getting a Bachelor's degree in computer science in the indefinite future, you might want to take a look at Computer Science and Artificial Intelligence program in our university administered by JetBrains.

UPD. Scoring distribution: $$$500 + (1000+500) + 1750 + 2250 + (2500 + 1500)$$$

UPD2. Congratulations to the winners:

Div 2:

1. rainboy

2. GidrAcH

3. toma_ariciu

4. biximo

5. zhengjc

Div 1 + Div 2:

1. tourist

2. Ormlis

3. potato167

4. risujiroh

5. kotatsugame

UPD3. Editorial.

Hello Codeforces!

I have the pleasure of inviting you to participate in Codeforces Round 960 (Div. 2), which will start on Jul/20/2024 17:35 (Moscow time).

The problems were prepared and authored by wuhudsm.

You will be given 6 problems and 2 hours to solve, one of the problems is divided into two subtasks.

One of the problems may be interactive. So, please refer to the guide on interactive problems if you are unfamiliar with them.

I would like to thank:

• Akulyat for coordinating the round;
• BurnedChicken for the only LGM testing;
• physics0523, liympanda, culver0412, Dominater069, TheScrasse, Andreasyan,satyam343 for GM and IGM testing;
• Error_Yuan, IanISam, Little_Sheep_Yawn, NemanjaSo2005, aufannn, IceKnight1093, and pavlekn for M and IM testing;
• Muhammad-Saram, vikram108, PROELECTRO444, htetgm, n0sk1ll, and AkibAzmain for CM testing;
• kHarsh3715, beyondpluto, larush, AdityaTakkar, Banis,Abhishek_Srivastava, Yugandhar_Master, chromate00, and astilate for Expert testing;
• md_nihal, HexShift, and dazlersan1 for Specialist testing;
• yash_04, and ishaandas1 for the Pupil testing;
• -2.71, and Binary_Thinker for the Newbie testing;
• tibinyte for the Illegal newbie lying face testing;
• MikeMirzayanov for the great Codeforces and Polygon platforms;
• CHATGPT for solving $$$0$$$ problems : ) ;
• And at last but not least, You for participating in the round!

Good luck and have fun!

Score distribution: $$$500 - 1000 - 1500 - 1750 - (2000+750) - 3000$$$

UPD:

Editorial

Congrats for the winners!

Div 2:

1. 0101byc

2. Psychotic_D

3. roIandpetrean

4. skahl15

5. thawin.ice

Div 1+Div 2:

1. tourist

2. jiangly

3. noimi

4. Sugar_fan

5. 0101byc

Hello, Codeforces!

I am pleased to invite you to participate in Codeforces Round 959 sponsored by NEAR (Div. 1 + Div. 2), which will be held at Jul/18/2024 17:35 (Moscow time). You will be given 8 problems and 2 hours to solve them. It will be rated for all participants.

The theme of the round is computer games!

Tasks for the round were prepared by EJIC_B_KEDAX, zwezdinv, green_gold_dog, molney, azureglow and Sokol080808.

We would like to thank everyone who assisted in the preparation of this round:

1. Our coordinator 74TrAkToR for his useful advices and help in preparing the tasks!

2. Qwerty1232 for red interest in testing the round.

3. turmax for the red-black testing.

4. makrav, arbuzick, Anonymous_Noob, Hyperbolic for red testing.

5. ivan.alexeev, alenenok, Kihihihi, azureglow, pakhomovee, plagues, IzhtskiyTimofey, FelixArg, XaRDKoDblCH, meowcneil, AndreyPavlov, djm03178, MylnikovNikolay for yellow testing.

6. Mr_Ell, krigare, marzipan, TimVen74, coder8080, MichsSS, PieArmy, tvladm, Vladosiya, bashem for purple testing.

7. Algolagon, PoDuReMaN, zarubin, IgorA, leoper, kovir_aleksey_korroy, Kosya, Vamperox for blue testing.

8. MakGeoKar, viteli for cyan testing.

9. Sonya_2009, ishaandas1 for green testing.

10. MikeMirzayanov for the excellent Codeforces and Polygon systems.

I also congratulate green_gold_dog on his birthday and wish him good luck on IOI.

This round is supported by NEAR!

NEAR was founded in 2017 by Illia Polosukhin, one of the creators of Transformers, and Alex Skidanov as an attempt to build an artificial system capable of solving competitive programming problems. You can read more about that attempt here.

Ultimately, NEAR pivoted into building a blockchain protocol, which it launched in 2020.

This year, NEAR started NEAR.AI, a new lab with a mission to build AI systems that are open and available to everyone, instead of being controlled by a few mega-corporations.

One of the areas of focus is making models capable of reasoning reliably, and for that, competitive programming problems provide a great environment. To help us build it, we invite all members of the Codeforces community with a rating of Specialist or higher (1400+) to help us annotate step-by-step explanations of solutions to competitive programming problems. We want to annotate a very large set of problems of all difficulty levels, and pay relatively high rewards in NEAR per annotation. You can join the system following this: https://codeforces.me/settings/near-connect-account

Thanks to NEAR for providing the following prizes to the contestants:

• 1st place: 512 Ⓝ;
• 2nd and 3rd places: 256 Ⓝ each;
• 4th to 7th places: 128 Ⓝ each;
• and so on;
• 512th to 1023th places: 1 Ⓝ each.

Score distribution: $$$500-1000-1250-2000-2000-2500-2750-3750$$$

Good luck!

UPD: Editorial

UPD2: Congratulations for the winners:

1. tourist

2. ecnerwala

3. orzdevinwang

4. Egor

5. jiangly

Hi.

In Spring semester, I conducted a short course titled “Dynamic Programming” in SPbSU. To complete the course, the students solved many training problems, and also prepared their own problem in Polygon.

For the majority of the students, it was the first problem they authored. Nevertheless, the result looks cute. A couple problems went to local contests. From the remaining ones, I composed two trainings and put them on Codeforces. The trainings are set at the following time:

• first: Dynamic Programming, SPbSU 2024, Training 1, starts on Jul/06/2024 11:30 (Moscow time), duration: 3 hours (statements, results, tutorial)
• second: Dynamic Programming, SPbSU 2024, Training 2, starts on Jul/07/2024 11:30 (Moscow time), duration: 3 hours (statements, results, tutorial)

Each training contains both easy and hard problems. The majority of the problems are intended for training. I think orange participants and below will have enough problems for the duration. The problems go in randomized order.

Good luck!

Hello Codeforces!

I am glad to invite you to Codeforces Round 958 (Div. 2) which will start on 15.07.2024 17:35 (Московское время).

The contest will last for 2 hours with 6 tasks for you to solve. The contest will only be rated for those with a rating not higher than 2099, but high-rated competitive programmers are also more than welcome to participate out of competition.

The score distribution is: 500-1000-1000-2000-2500-3500

The contest will be impossible without the help from:

• 244mhq for wonderful coordination.
• gyh20, Dominater069, Um_nik, A_G, omeganot, tkl2006, harsh__h, oursaco, Hori, kostia244, ishaandas1, maomao90, waidenf, Stefan2417, MisterReaper for testing.
• MikeMirzayanov for Codeforces and Polygon.

Good luck and have fun!

Update: editorial

Update: video editorial

Hi everyone!

A week ago, the 2nd edition of the Western European Olympiad in Informatics was held in London, UK, and now we've brought the problems for everyone to solve on Codeforces! The mirror contest will be held on the Codeforces Gym on Sunday $$$14^{\text{th}}$$$ July 2024 at 10am UTC+1 (check your timezone here!).

Please don't participate in the mirror contest if you have participated or seen the problems!

The Western European Olympiad in Informatics is an individual contest for top secondary school students from Belgium, France, Ireland, Italy, Luxembourg, Netherlands, Portugal, Spain, Switzerland and United Kingdom.

The contest consists of a single day; contestants are given 5 hours to solve 4 problems of various difficulty. Each problem is worth 100 points, distributed into multiple subtasks with different constraints that allow the participant to earn partial scores. For testing, the IOI grading format is used, where the participant receives full feedback about the execution of the solution on all tests during the contest. C++ is the only allowed language in this contest.

We hope you enjoy the contest!

• WEOI 2024 Committee & Contributors

FelixMP hugopm I_love_MikhailRubinchik ScarletS veluca93, Ahmadsm2005 Bakry erekle

Hello, Codeforces! We are pleased to invite you to Codeforces Round 957 (Div. 3), which will be held on Jul/11/2024 17:35 (Moscow time).

The round will be hosted by rules of educational rounds (extended ICPC). You will be offered 7 problems, which I with Noobish_Monk, ErnKor, Kmes and ArSarapkin have prepared for you.

The rules of the third division are:

• The penalty for a wrong submission is 10 minutes.

• 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.

Reminding you, that only trusted participants of the third 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 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 (or you are a newcomer/unrated), then the round will be rated for you.

We would like to thank everybody, who helped in preparing this round:

• Our coordinators, Gornak40 and Vladosiya for a wonderful coordination!

• MikeMirzayanov for wonderful Polygon and charming Codeforces!

• Vladosiya for deleting the lore in almost all of the problems...

• Our numerous testers: natalina, FairyWinx, Kosya, ErnKor, 74TrAkToR, ArSarapkin, mainyutin, senjougaharin, gaiercop, mikeamir0310, Maksim_Musikhin, Arina77, artimovich.ko, main-scobik, savanzh, petr_davydov, Pronkin_dv, kalita.georgy, kuznetsov.da, s_w_a_n_i_k, Keopint, VolkovMA, kuewa, cry, Harsh_kunwar, Kon567889, dshindov, OAleksa, SajidAbdullah, fishcurry, george_the_piggy, k1sara and many others, who didn't mention their handle.

• Special thanks for KEFedorov, for inviting more than 35 testers.

Good luck!

UPD1 After the end of the round, Shayan will broadcast the solutions, a recording will also be available, but we will also prepare a textual editorial.

UPD2 Video Discussion by Shayan

UPD3 Video of solving the round + Editorial by the "winner" of this round, neal

UPD4 Editorial.

UPD5 Congratulations for the winners:

Official:

1. siiiuuuuuuu

2. shil_pelmen

3. xiojoy

4. _Separation

5. son_and_moon

Official + Unofficial:

1. tourist

2. neal

3. Dominater069

4. abc864197532

5. hitonanode

Hello, Codeforces!

NJACK — the Computer Science Club of IIT Patna is excited to invite you to Codeforces Round 956 (Div. 2) and ByteRace 2024 under Celesta — the annual Techno-Management Fest of IIT Patna.

The contest will take place on Jul/07/2024 17:35 (Moscow time). This round will be rated for participants with rating lower than 2100.

Many thanks to all the people who made this round possible:

• The problems were authored and prepared by AwakeAnay, ShivanshJ, TimeWarp101, DC17, BlazingDragon, Swap-nil, Pew_Pew. and me.
• Special thanks to ScarletS for coordinating the round (and not killing me)!
• A big shoutout and thankyou to Alexdat2000 for providing the Russian translations.
• Thanks 2.0 to ScarletS for having improved the experience of other CF users over the years.
• Special mention to mayankfrost and quantau for their guidance and moral support.
• A_G, Andreasyan, maomao90, CSQ31, fishy15, eggag32, MateoCV, Evirir, bananasaur, satyam343, jat.arc2004, chromate00, hashman, Nishant_K, Ali_cs7, Patel45, Newtech66, CIXTEEN, braman, 7oSkaaa, Edward4762, LucaLucaM, waidenf, yoyo0869, priyanshu.p and ishaandas1 for testing and providing detailed feedback that improved the quality and balance of the round significantly.
• Our lord and saviour MikeMirzayanov for great systems Codeforces and Polygon.

You will have 2 hours 15 minutes to solve 7 problems.

UPD: Scoring Distribution: 500 — 1000 — 1250 — 1750 — 2000 — 2500 — 3000

UPD: Editorial

UPD: Congratulations to the winners!

Top 5 (Div 2):
1. _worst_
2. Shirayuki_Noa
3. cynNYCal
4. cocae
5. _furina

Top 5 (Div 1):
1. neal
2. jiangly
3. BurnedChicken
4. turmax
5. Sugar_fan

About Celesta

Celesta is the annual Techno-Management Fest of IIT Patna. Celesta conducts a variety of events in various technical domains. Some of these are open and free for all, with exciting prizes and goodies for the winners!

You can head over to our website and check it out for yourself!

We have had the 2023 edition of ByteRace hosted on Codeforces too. Feel free to have a look: Codeforces Round 845 (Div. 2) and ByteRace 2023

Good luck!