Hello Codeforces!

On Jun/25/2022 17:35 (Moscow time) we will hold Codeforces Global Round 21.

It is the third round of a 2022 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2022:

• In each round top-100 participants get points according to the table.
• The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
• The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2022 supported the global rounds initiative!

All problems except one are authored and prepared by me. The other problem is authored by gyh20.

We would also like to thank the following people:

• irkstepanov for coordination, and KAN for helping as well.
• gyh20, ShuiLaoshi, ilyakrasnovv, fengzhengwei, Vladithur, antontrygubO_o, Golovanov399, snowysecret, ak2006 for testing.
• MikeMirzayanov for polygon and codeforces.

Round information:

• duration: 2 hours and 15 minutes
• number of problems: 8
• score distribution: 500-1000-1500-2000-2000-2500-3250-4000

We are looking forward to your participation!

Upd Editorial https://codeforces.net/blog/entry/103479

Upd Winners!

1. ksun48
2. jiangly
3. Um_nik
4. Petr
5. maroonrk

Hi!

This Sunday will take place All-Russian olympiad for students of 5-8 grades, in the name of Keldysh. Good luck to all the participants! Olympiad is conducted under the guidance of the Moscow Olympiad Scientific Committee, in particular GlebsHP, ch_egor, Endagorion, vintage_Vlad_Makeev, Zlobober, meshanya, cdkrot, voidmax, grphil, fedoseev.timofey and, of course, Helen Andreeva.

We are happy to announce the Codeforces Round #802 based on the problems of this olympiad! It will be a Div. 2 round, which will take place at Jun/19/2022 12:05 (Moscow time). You might have already participated in rounds based on the school olympiads, prepared by Moscow Olympiad Scientific Committee (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583, 594, 622, 626, 657, 680, 704, 707, 727, 751, 775). Please notice the unusual time.

The problems of this olympiad were prepared by Siberian, _overrated_, Igorbunov, Ziware, talant, king-pankevich.acoolguy under the supervision of fedoseev.timofey.

Thanks to RedMachine-74 for their help in organizing the Codeforces version of this contest and one of the problems, MikeMirzayanov for the Codeforces and Polygon.

Also I would like to thank the Tinkoff company and personally Tatyana TKolinkova Kolinkova for great help with organizing the competition.

Thanks to NEAR for supporting this round, details can be found in this post.

Good luck!

UPD1: Thanks to Um_nik, 244mhq, MichsSS, zarubin, TeaTime, devid, Mangooste for testing.

UPD2: Scoring distribution: 500 — 1000 — 1500 — 1750 — 2500 — 3000

UPD3: Winners!

Div. 2:

1. teacherone
2. zsxdcfv
3. AndrescuIII
4. rhzmydd
5. Yuki991

Div. 1 + Div. 2:

1. SSRS_
2. noimi
3. Fysty
4. peti1234
5. teacherone

UPD4: Editorial

Hi, Codeforces!

We welcome everyone to take part in Codeforces Round 801 (Div. 2) and EPIC Institute of Technology Round, which will start on Jun/18/2022 17:35 (Moscow time).

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

You will be given 5 problems and 2 hours to solve them. One problem will consist of multiple subtasks.

The score distribution will be 500 — 750 — 1250 — (1250+1000) — 3000.

The round was prepared by me, ki0apa, and akifpatel.

We would like to say a word of appreciation:

• to antontrygubO_o for amazing coordination of the round
• to 18o3, bobbilyking, brunovsky, BucketPotato, dbaumg, fishy15, jonathanh8686, Max_Calincu, 244mhq, naman1601, richardkyu, rivalq, satyam343, timreizin, Vladik, vilcheuski for testing the round
• and of course, to MikeMirzayanov for the Codeforces and Polygon platforms.

Good luck to all the participants!

Update: Editorial is out!

About EPIC Institute of Technology

Recently, in our blog, we have introduced the educational project of EPAM called EPIC Institute of Technology.

EPIC Institute of Technology, a part of EPIC — EPAM Product Innovation Center, is truly a unique educational project driven by the Deltix team under the EPAM Systems umbrella.

Why EPIC:

EPIC Institute of Technology is an accelerator for the best talents. Our students will acquire hands-on experience in one of the selected major programs, all of them are highly demanded right now on the top projects, together with the fundamental knowledge, so indispensable for real professionals. Successful graduates will have a unique chance to jump start their career on the most challenging and interesting EPAM projects worldwide. You will join the community of intelligent and driven individuals and have an honor to work with and learn from them.

Here are the answers to the most common questions:

How much does education cost?

EPIC Institute of Technology is completely free. There are no fees to register for exams or tuition fees.

How is the educational process organized?

Each program lasts exactly one year. The academic year consists of two semesters. Courses in the first semester are the same for all programs. Courses in the second semester depend on the selected major program.

Students will take an intermediate assessment in the middle of the semester. The final grade will be given for each course at the end of each semester. The grade a student gets for each training course, depends on the quality of the laboratory work and participation in lectures and practical classes.

Lectures, practical classes, seminars, conferences, and other interesting activities are provided for students on all training courses.

How will the classes be held?

All classes will be held online. Lectures and practical classes will be held at the specified time according to the provided schedule. Recordings of all classes will be available for those students who, for any reason, were not able to attend.

In what language will I study?

All programs are in English language.

What will happen after graduation?

EPIC Institute of Technology graduates will get a diploma and an offer to join, either as an intern or a full-time position, one of the hot EPAM projects where skills acquired at EPIC Institute of Technology will be demanded.

Please visit our website to learn more about EPIC Institute of Technology and the available programs. If you have any questions, you can quickly ask them in our chat.

Hi Codeforces!

Keshi, alireza_kaviani and I are delighted to invite you to participate in Codeforces Round 800 (Div. 1) and Codeforces Round 800 (Div. 2).

• Start time: Jun/16/2022 17:35 (Moscow time)
• Duration: $$$120$$$ minutes
• Number of Tasks: $$$6$$$ for both divisions
• Rated range: ($$$-\infty$$$,$$$1899$$$] for Div2, [$$$1900$$$, $$$\infty$$$) for Div1

We are honored to have set the 800th Codeforces round. We wish this wonderful platform all the best along with many other exciting rounds.

Huge thanks to the following people:

• antontrygubO_o for his breath-taking coordination.

• Our testers Um_nik, errorgorn, Koosha_Mv, irkstepanov, ymmparsa, sohsoh, fatemetmhr, Dorost, nor, pooya-shams, Arnch, Kahou and mosaev for testing the round and providing invaluable feedback.

• radiohead because we got inspiration from them while coming up with task names.

• MikeMirzayanov for the amazing platforms Codeforces and Polygon!

• Last but not least, to all the participants of this round!

Thanks to NEAR for supporting this round, details can be found in this post.

We have worked hard to keep the statements clean and the pretests strong!

Please read all of the problems and their notes, enjoy your time and solve as many as you can! Good luck have fun to everyone!

The scoring distributions will be announced later.

UPD: Here are the scoring distributions:

• Div. 1: 750 1000 1500 2250 2500 3000

• Div. 2: 500 1000 1500 1750 2250 3000

UPD: Editorial is out!

Hello!

I always like to think that Codeforces is not only a place where you come to compete but also a place where you can learn. Learn new things.

Two years ago, we launched the EDU subproject, a platform for publishing classes. There are already several classes, but there are so many interesting topics around!

The Codeforces team can write the platform, make the technical foundation, but it would be great to write content with the support of the community.

Thanks to the support of competitive programming alumni, we have a budget for targeted grants for the preparation of new classes in the EDU section. Hope we have new content soon!

We are looking for lesson authors who could prepare and record one or more lessons. Those who are now red or have ever been red are invited.

We assume that one lesson (class) consists of:

• 3-5 steps: break the lesson into logical parts,
• video materials explaining the topic (usually, the total duration is 60-120 minutes),
• text summary
• a thematic training set of problems with a wide range of complexity (from the most basic on this topic to quite tricky ones)
• first of all, we would like to cover the main topics of competitive programming — DP, graphs, basic data structures, etc.

Please note that we expect you to record and edit the video by yourself. Look at already recorded lessons to understand the expected format and structure of lessons. We have a rich history of teaching, so you can count on our advice and assistance in preparing lecture plans and problems. If video editing scares you, then here we can help.

We invite you to help grow the community and make history. I am sure that the recorded classes will be watched by tens of thousands of people (or more?).

The reward for recording one class is $1000.

If you are now red or have ever been red and you are interested in this offer, then fill out the form (open until June 28th).

Hello Codeforces!

mesanu, flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 799 (Div. 4)! It starts on Jun/14/2022 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 the testers: Neophiliatic, Qualified, sandry24, _Anurag, jampm, TimDee, Olympia, sparkles, AlperenT, BucketPotato and VIP-tester _Vanilla_.

And thanks to NEAR for supporting this round, details can be found in this post.

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

Good Luck!

UPD: Editorial is posted!

Hello Codeforces!

On Jun/12/2022 17:35 (Moscow time) Educational Codeforces Round 130 (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, Vladimir vovuh Petrov, 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:

Hey, Codeforces!

We are thrilled to announce an amazing work & study opportunity with Vodafone.

Vodafone Group has partnered with Harbour.Space University to offer Bachelor's and Master’s degree scholarships in Computer Science, Data Science, Cyber Security and Front-end Development as well as MBAs and work experience in one of the leading UK telecommunication companies.

Vodafone Group is opening a new technological HUB in Malaga, an international center of excellence dedicated to research and development of technical solutions, such as Secure Networks, 5G and 6G development, Open RAN, IoT, MPN & MEC and UCC for Vodafone Business, platforms and enterprise solutions.

We are looking for various junior to mid level positions (or senior) to fill in different fields such as:

• Front-end Development
• Full-stack Development
• Backend Development
• Technical Architecture
• Enterprise Architecture

APPRENTICESHIP REQUIREMENTS

General Requirements:

• High School Diploma or Bachelor's Degree with prior work experience
• CV or LinkedIn Profile (your Codeforces rank has to be added to your CV)
• Proficiency in English (Spanish is a plus)

Requirements for Frontend Developer:

• At least 1-3 years of experience in Angular.
• At least 1-3 year of experience working in React.
• Strong knowledge of web platform fundamentals: HTML, JavaScript and CSS.
• Design and implementation of low-latency, high-availability, and performant applications
• Definition / construction of CI / CD pipelines using tools such as Jenkins, Sonar, Kiuwan.

Requirements for Full-Stack Developer:

• Minimum 3 years of proven experience in platform development (CDI/DevOps based environment). With one or more of the following:
• Java SE/ Javascript
• Scripting languages, i.e. python, perl, shell scripts.
• Proven experience in backend & frontend software systems & web applications.
• Proven experience with HTPP, MQTT, LwM2M, Kafka, various databases (SQL and non-SQL).
• Proficiency in cloud-native development.
• Hands-on experience with CDI tools.

Requirements for Java Developer:

• Industry experience with Software Platforms in Linux, on-premises and cloud
• Solid understanding of server technologies
• Strong academic knowledge and professional experience of software development: Java Enterprise, Oracle, Linux, Windows
• Good understanding of system monitoring tools and automated testing frameworks
• Experience with SQL, XML, JSON and CSV
• Experience of providing and maintaining transformations and APIs for customers and partners
• Good understanding of Databases – Oracle, MongoDB, ElasticSearch.
• Good understanding of java frameworks, SpringBoot, Spring technologies
• Good understanding of container systems (docker) and orchestrators (docker compose, Kubernetes) and messaging technologies, kafka, rabbitmq
• Good understanding of Unix shell, Perl, python to perform automation and maintenance tasks and CI/CD environments
• Educated to BSc degree level in telecommunications or related discipline with Software Development experience

Good luck on your round, and see you next time!

Harbour.Space University

UPD: Editorial is out

Hello Codeforces!

We are glad to invite you to Codeforces Round 798 (Div. 2) which will start on Jun/10/2022 19:35 (Moscow time). Please notice the unusual time. You will be given 5 problems and 2 hours to solve them.

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

All problems are prepared by n0sk1ll and me. We would like to thank:

• TheScrasse, nor, Riblji_Keksic, AlperenT, Sarvesh10 for testing this round and providing valuable feedback!
• DmitryGrigorev for coordinating!
• MikeMirzayanov for creating amazing Codeforces and Polygon platforms!

Thanks to NEAR for supporting this round, details can be found in this post.

We are looking forward to your participation!

Score Distribution:

$$$500-750-1250-1750-2500$$$

UPD: Editorial

Hello! Codeforces Round 797 (Div. 3) will start at Jun/07/2022 17:35 (Moscow time). You will be offered 6-8 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 ACM-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 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) 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.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of our work. Problems have been created and written by ITMO University teams: MikeMirzayanov, MisterGu, myav, Gol_D, Aris, senjougaharin, me Vladosiya.

Also many thanks to I_love_teraqqq , allvik66 , Fortin , Artem_Sukharev , vsinitsynav , yorky , oversolver , majorro , ilya_totl , Undying , olya.masaeva , Kniaz , Golovanov399 , farmerboy , Absyarka , Kavaliro , neeraj_joshi for testing the contest and valuable feedback.

Good luck!

UPD:Editorial

Hi Codeforces! Happy Dragon Boat Festival!

We are glad to invite you to our first Codeforces Round Codeforces Round 796 (Div. 1) and Codeforces Round 796 (Div. 2) which will be held on Jun/03/2022 17:35 (Moscow time). This round will be rated for participants of both divisions. Participants in each division will be offered 6 problems and 2 hours to solve them. The two divisions will share 3 problems.

In this round, as the best friend of the characters in Touhou Project, you are going to help them solve the problems they meet.

The problems are prepared by xiaoziyao, Yakumo_Ran, SSerxhs, Cocoly1990, LilyWhite, Elegia and me. We hope you will enjoy this round.

Great thanks to:

• RedMachine-74 for good coordination of this round and translating all statements to Russian,
• Yakumo_Ran for providing most tasks,
• SSerxhs for preparing most tasks,
• LilyWhite for polishing statements,
• Elegia, QAQAutoMaton, jqdai0815, Kevin114514, Suika_predator, loveye, Serval, ix35, Miko35, mrsrz, SanweiTreap, Eden_CY,wind_whisper,xuezhe, Cocoly1990, KaguyaH, meowcneil, plagues, marzipan, nhc, SCL_, zarubin for testing our round,
• KagamineRin, huhaoo, juju054, JohnVictor and Zcusss for other help,
• MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• NEAR for supporting this round, details can be found in this post.

Please pay attention that there will be no more than 998244353 interactive problems in this round, so learn more about interactive problems here before the contest.

Good luck & Have fun!

UPD 1:

Score Distribution:

Div2: $$$500 - 750 - 1250 - 1500 - 2000 - 3000$$$

Div1: $$$500 - 750 - 1500 - 1500 - 2000 - 3000$$$

UPD 2:

Editorial is out.

UPD 3:

Winners

Div.1:

1. Um_nik
2. heuristica
3. jiangly
4. tourist
5. SSRS_

Div.2:

official:

1. Hanasaki
2. tkended
3. boboGM_when
4. a_nanas
5. rondoudou

unofficial:

1. Teating_
2. AgafonovArtem
3. luogubot
4. znqd3116
5. XiShui_AKIOI