Happy Easter, Codeforces! Sadly the round will not be Easter themed :(

We (arvindf232, culver0412, snowysecret, potatoo, jerryliuhkg) are delighted to invite you to participate in Codeforces Round 865 (Div. 1) and Codeforces Round 865 (Div. 2), which will take place on Apr/09/2023 17:45 (Moscow time). Participants with a rating lower than 1900 will participate in Division 2, while participants with a rating of at least 1900 will participate in Division 1. Notice the unusual starting time.

All the problems were authored and prepared by arvindf232, culver0412, snowysecret and potatoo. Huge thanks to the following people, without whom the round would not be possible:

• Artyom123 for excellent coordination and translation of statements.
• KAN for help with round preparation.
• jerryliuhkg for problem proposals which didn't make it to the final problem set.
• gamegame, dorijanlendvaj, abc864197532, ShuiLaoshi, ACGN, Rekaxem, xiaoziya, Perpetually_Purple, prvocislo, Qingyu, JeffreyLC, wyhong3103, Nahian9696, NemanjaSo2005, Dakto, triple__a, Singinginginging, Imakf, Ritwin, TomiokapEace, dbscts, mariowong123, jerryliuhkg, Flower08, Codula, prabhav_, rsj, __jk__, Aaeria, DBSHoShunNgai, Tutis, competitive__programmer for testing and valuable feedback.
• rsj for providing a nicer solution to one of the problems.
• MikeMirzayanov for Codeforces and Polygon platforms.
• You, for participating!

In both divisions, you will have 2 hours and 15 minutes to solve 6 problems. One of the problems is interactive, please see the guide of interactive problems if you are not familiar with it.

Wish you good luck and high ratings!

UPD1: Score distribution is as follows:

• Div. 1: 500-1250-1750-2500-3000-3500
• Div. 2: 500-1000-1250-2000-2500-3250

UPD2: Editorial

UPD3: Congratulations to the winners!

Hello, Codeforces!

AC-Automation and I rui_er are glad to invite you to participate in Codeforces Round 864 (Div. 2), which will be held on Apr/08/2023 17:05 (Moscow time). Please note the unusual start time.

This round is rated for the participants with ratings strictly lower than 2100. You will be given 6 problems and 2 hours to solve them. All the problems are prepared by AC-Automation and me.

We would like to thank:

• darkkcyan for a perfect coordination and help with the problem preparation.
• AC-Automation for providing some rejected problems and helping me a lot in preparation.
• zplqwq for polishing English statements and editorials.
• Alexdat2000 for the Russian translations.
• N_z__, HQJ2007, 2_3_3, ShmilyTY, constructive, fishy15, Celtic, 10circle, LXH-cat, Hanghang007, wsc2008qwq, KaguyaH, XG0000, Astolfoo, 5ab, Electric_Field, MagentaCobra, RedLycoris, Everule, ieeqwq, Dominater069, Sol1, happydef, geospiza, amenotiomoi, zengminghao, yoy68, .Miikka., aberter0x3f, vectorwyx, vinfat, AliceLiCF, le0n and competitive__programmer for testing this round and providing valuable feedbacks.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

• You

  for participating in this round.

There will be a finite number of interactive problems, so please see the guide of interactive problems if you are not familiar with it.

The main character of the problems is Li Hua.

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

This is our first round. We've tried our best to make the round enjoyable. We are looking forward to your participation and hope you gain a non-negative delta in this round.

UPD1: Score distribution: 500 — 1000 — 1500 — 1750 — 2250 — 3000.

UPD2: Editorial is out.

UPD3: Statement in Chinese and Editorial in Chinese are out.

UPD4: Congrats to the winners!

Div.2:

1. syf2008
2. elizazh
3. zhouzizhe
4. psz1
5. wnmrmr

Div.1 + Div.2:

1. jiangly
2. heno239
3. SSRS_
4. BurnedChicken
5. Sugar_fan

Also congrats to the only div.2 participant who solves problem F: reborn2023!

Hello Codeforces!

On Apr/06/2023 17:35 (Moscow time) Educational Codeforces Round 146 (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:

Hey, Codeforces!

Once again, it is time for another exciting scholarship opportunity from Harbour.Space!

We are looking for talented individuals who want to launch their careers in Cyber Security with a 50% scholarship to study in Barcelona.

If you love technology and looking for an exciting career, then Cyber Security might be for you!

But don't just take our word for it — as a member of the Codeforces community, you know the value of continuous learning and growth. The Cyber Security master’s programme at Harbour.Space responds to a growing market need, driven by increasing threats of global cyberwarfare, for cyber professionals with advanced training in both defensive cybersecurity and offensive cyber actions. The programme is designed to provide the knowledge, skills, and abilities required to perform critical cybersecurity tasks successfully.

Requirements:

• Bachelor’s Degree
• Professional fluency in English
• Your CV in English

What you will learn:

• Applied Threat Intelligence
• Threat Hunting
• Reverse Engineering and Malware Analysis
• Digital Forensics and Incident Response
• Pentesting and Ethical Hacking
• Hardware Conception of Processing Modules for the IoT
• Networks and Protocols
• Crisis Management and Communications
• BlockChain and IAM
• Soft Skills: Team Building, Presentation Skills and Meeting Facilitation
• And more

Make sure to apply before April 30th, 2023, to be eligible for the scholarship and reduced application fee.

Keep in touch and follow us on LinkedIn for more scholarship opportunities. And follow us on Instagram to evidence student life, events, and success stories from students.

We are always happy to see Codeforces members join the Harbour.Space family.

Apply now to learn from the best in the field and take your career to the next level!

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

Harbour.Space University

UPD: The contest is unrated. We apologize for the inconvenience.

UPD: Editorial is out

Dear Codeforces,

I am honored to share that the IX-th edition of the AGM International Programming Contest has officially begun!

AGM is addressed to High School students who compete in teams of up to 3 members, ICPC-style. The contest has 2 rounds:

1. The Qualification Round held online, on Saturday, the 22nd of April between 15:00 and 20:00 GMT+3 (timeanddate)
2. The Final Round held onsite, hosted by ICHB in Bucharest (Pallady Campus). The date and time will be announced soon.

Registrations are opened until Thursday, the 20th of April at 17:00 GMT+3: https://forms.gle/ViXe3VwpA1gLm1uW6

The problem sets are entirely developed by current and former university students from the United Kingdom, Romania, and the Netherlands.

The top 10 teams of the Final Round will receive Diplomas. Additionally, the top 3 teams of the Final Round will receive cash prizes:

• I-st place: 1200 RON
• II-nd place: 900 RON
• III-rd place: 600 RON

In the meantime, please have a look over the last three years' problem sets here.

Here are some useful links:

• Website: https://agm-contest.com
• Facebook: @AGM.Contest
• Competition Rules: https://agm-contest.com/competition-rules
• E-mail address: [email protected]

Finally, I am more than delighted to present our team: patrick.sava (the heart of the project), teoionescu, carabet.cosmin, Mihai22e, Stelutzu, munteanuvlad98, caesar2001, MiricaMatei, tinca_matei, georgerapeanu, average_frog_enjoyer, popovicirobert, Alex18mai, ionan6ix, butasebi, Stefan_Radu, eman98, mihaicristian, and me

We are looking forward to welcoming everyone!

Kind regards,

George

Hello! Codeforces Round 863 (Div. 3) will start at Apr/04/2023 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 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 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 team: MikeMirzayanov, myav, Aris, Gornak40, KwisatzCoderach and Vladosiya.

We would like to thank: Sugar_fan, doreshnikov, powergee101, pashka, KseniaShk, RedMachine-74, stefanbalaz2, playerr17, diskoteka, FiniteMoves, nigus, erankyun, plourde27, Be_dos, donghoony, lucasxia01, Jostic11, sansen, gigabuffoon, akulenok, pwned, vrintle for testing the contest and valuable feedback. List of testers will be updated.

Good luck!

UPD: Editorial

Hello, everyone at Codeforces.com!

In this round, I (Alexdat2000) and two of my friends — FairyWinx and sevlll777 — prepared 6 problems for you (one of which is divided into two subtasks), and you will have 2 hours to solve them. Everyone is welcome to follow the link: Codeforces Round 862 (Div. 2) at Apr/02/2023 17:35 (Moscow time). This round will be rated for all participants with a rating of strictly less than 2100.

And now a few acknowledgements:

• Thanks to [Coordinator] pashka for coordinating and helping with testers

• Special thanks to [G.O.A.T.] Mangooste for discussing tasks and testing

• Thanks to all the testers: [MVP++] Ormlis, [Upsolver] physics0523, [Upsolver] Vladithur, [Upsolver] vsinitsynav, pashka, Dominater069, darkkcyan, AlperenT, rsj, NewLul, Sweezy, KiruxaLight, gmusya, aryan12, tomsangotw, jonatas57, ivn1k, vefg, putis, DDima, 9kin, Dmitry345, competitive__programmer, playerr17 и KodomoTachi

• Thanks to MikeMirzayanov for the Codeforces and Polygon platforms

• TeaTime

• Thanks Artyom123 for the initial task review

Scoring distribution: 500 — 750 — 1250 — 1750 — 2250 — (1750 + 1750).

UPD: Editorial

UPD-2: Congratulations to the winners of the round!

Top 5 official participants:

Place	Participant	Problems solved	=
1	b6e3	6	6987
2	Darren0724	6	6683
3	cpbeginner	6	6520
4	suckthembi	6	6269
5	GOD_0F_DEATH	6	5915

Top 5 of all participants:

Place	Participant	Problems solved	=
1	jqdai0815	7	8214
2	SSerxhs	7	7786
3	Sugar_fan	7	7750
4	maspy	6	7623
5	noimi	6	7255

Participants who sent the first correct solution to the problems:

Task	Participant	Penalty
A	A_G	0:00
B	Geothermal	0:02
C	BucketPotato	0:08
D	peti1234	0:11
E	b6e3	0:11
F1	BeyondHeaven	0:26
F2	SSerxhs	1:37

Hello, Codeforces!

I, along with AlperenT, Ari, BucketPotato, ScarletS, and ToxicPie9, would like to invite everyone on Codeforces to the April Fools Day Contest 2023! The 11th April Fools Day Contest will take place on Apr/01/2023 17:35 (Moscow time). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.

Please note that the round is unrated.

In this round you'll be given $$$n$$$ weird problems and 2 hours to solve them, where $$$7 \leq n \leq 12$$$. At most $$$\sqrt{n}$$$ of the problems will be interactive. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them).

You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2020, 2021, 2022.

Good luck, and have fun!

UPD1: Thanks willy108 for testing!

UPD2: The editorial is released!

UPD3: Congrats to the winners!

1. InternetPerson10
2. Geothermal
3. A_G
4. Maksim1744
5. LJC00118

And congrats to the first solvers!

• A: zscoder
• B: KeNaj712
• C: conqueror_of_tourist
• D: namcartoon06
• E: SanguineChameleon
• F: A_G
• G: lethan3
• H: InternetPerson10
• I: aberent (the only person who solved it in contest!)
• J: mxdcxt

UPD4: Sorry for the inconvenience, the contest is now open for practice submissions + virtuals.

Hello, Codeforces!

I'm very glad to invite you to participate in CodeTON Round 4 (Div. 1 + Div. 2, Rated, Prizes!), which will start on Mar/31/2023 17:35 (Moscow time).You will be given 8 problems and 2 hours to solve them. The round will be rated for everyone.

I'd like to give my sincere thanks to:

• RedMachine-74 for the wonderful coordination!

• furry for the help with the statements.

• Suika_predator, SSerxhs, apeiya, xay5421, NemanjaSo2005, applese, bxh520, fr200110217102, furry, MintBruce PaperCloud, CedeaT0, Kath1031, jcccc, dyxg, tzc_wk, xiaoziya, qiqi20021026, Pointy, HorizonWind, ilyakrasnovv, ShmilyTY, njupt_lyy, rsj,hzr, p_b_p_b, competitive__programmer, flakes24, Milesian, pb0207, _Vanilla_, EternalJourney, alwyn and MagicalFlower for testing the round.

• MikeMirzayanov for the great codeforces and polygon platform.

• You for take part in the round.

Hope everyone can enjoy the round!

UPD: The tutorial is here.

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 4.

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 4 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 4 and hope you enjoy the contest!

Greetings Codeforces community!

We are excited to announce the Constructor Open Cup 2023, our annual online programming competition organized by Constructor University and JetBrains.

What is the Constructor Open Cup 2023?

Constructor Open Cup is an online contest organized by Constructor University and JetBrains, the global leading tool provider for developers, to promote interest in computer science, data science, software development, and software engineering. You'll have to race against the clock to solve real-life programming challenges.

Put your knowledge and skills to the test in this 4-hour competition and stand a chance to walk away with a scholarship for the Bachelor's degree in Data Science and Software Development at Constructor University, Germany’s #1 private university*!

Constructor Open Cup timetable

• March 23-29, 2023 | Practice Round

Get familiar with the testing environment during this practice round. We highly recommend this optional step. Don’t worry: it won’t affect your final score!

• March 30, 2023 at 2 PM (UTC) | Main Round

You will have 4 hours to complete a series of algorithmic programming tasks of various difficulty levels.

Registration closes 1 hour before the start of the contest.

Prizes and Winner Announcement

The top candidates will receive exciting prizes, including:

• Chance to get scholarships for the Bachelor’s degree in Data Science and Software Development*
• Exciting memorable gifts from Constructor University and JetBrains

We're looking forward to seeing your programming skills on competition day, and we wish you the best of luck.

*The winners who applied to the BSc program in Data Science and Software Development will receive an email to schedule the interview with Constructor University professors and JetBrains.

Can I participate?

Everyone is welcome! The contest is open for all ages and skill levels, all you need is a passion for coding.

To get the chance for the JetBrains scholarship for Data Science and Software Development program, please check Constructor University’s eligibility requirements.

How can I participate?

• Register your details here.
• Register at Codeforces using the Login/Password you receive in the confirmation email.
• If you have any further queries, please reach out to [email protected].

Why should I join the Constructor Open Cup?

Previously known as ‘STAR Contest’, the competition attracted more than 1,600 contestants across 82 countries over the past three years. Renamed to Constructor Open Cup in 2023, this contest welcomes all regardless of age, qualifications, or skill level.

By participating in the Constructor Open Cup, you will:

• Get recognized by top science and technology leaders
• Pit your algorithmic problem-solving skills against competitors from other countries
• Get a chance to get a full scholarship for BSc program in Data Science and Software Development

Don't miss out on this exciting opportunity to challenge yourself and showcase your talents. Join the Constructor Open Cup today!

About the BSc Data Science and Software Development program

This program prepares talents to become tomorrow’s elites in software development, programming languages, data analysis, and machine learning. You will benefit from the latest insights and knowledge from top industry partners and get the right skills needed for these rapidly changing industries. Through real-world projects, the practice of the latest technologies, and the close mentoring of industry experts, you will gain a unique experience that sets you up for successful career opportunities. Learn more about the program here.

About Constructor University

Founded in 2001 as a private, English-language campus university, it repeatedly achieves top results in national and international university rankings. Its more than 1,600 students come from over 110 countries, and around 80 percent have moved to Germany to study. Research projects at the University are funded by the German Research Foundation, the European Union's Framework Program for Research and Innovation, and global leading companies.

About JetBrains

JetBrains creates intelligent software development tools used by over 15.9 million professionals and 90 Fortune Global Top100 companies. Its lineup of more than 30 products includes IDEs for most programming languages and technologies, such as IntelliJ IDEA, PyCharm, and others, as well as products for team collaboration, like JetBrains Space. JetBrains is also known for creating the Kotlin programming language, recognized by Google as the preferred language for Android development. The company is headquartered in Prague, Czech Republic, and has offices throughout the world. For more information, please visit https://www.jetbrains.com/