Hello Codeforces!

ijxjdjd and I are pleased to invite you to participate in Codeforces Round #728 (Div. 1) and Codeforces Round #728 (Div. 2) which will be held on Jun/25/2021 18:35 (Moscow time). Please note the unusual timing. Each division will have 5 problems and 2 hours and 15 minutes to solve them.

We would like to thank:

• adedalic for amazing coordination of our round!

• singleLOOP, skittles1412, penguinhacker, m371, growup974, dorijanlendvaj, qlf9, Nezzar, Tlatoani, hu_tao, Etherite, and prabowo for testing the round and providing invaluable feedback.

• MikeMirzayanov for the amazing platforms Codeforces and Polygon.

• You, for participating!

Read all of the statements carefully, and we hope you enjoy the problems! Wish you high ratings!

UPD: I would also like to thank Roberticey, golions, and kefaa2 for testing.

UPD: Here's the score distribution:

Div 1: 500 — 1250 — (1500 + 750) — 3000 — 3500

Div 2: 500 — 1000 — 1500 — 2250 — (2500 + 750)

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 and, of course, Helen Andreeva.

We are happy to announce the Codeforces Round #727 based on the problems of this olympiad! It will be a Div. 2 round, which will take place at Jun/20/2021 13:05 (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).

The problems of this olympiad were prepared by _tryhard, Siberian, shishin, Artyom123, TeaTime, Tikhon228 under the supervision of grphil.

Thanks to KAN, Aleks5d and isaf27 for their help in organizing the Codeforces version of this contest and 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.

Good luck!

UPD1: Thanks to _overrated_ and Ormlis for testing.

UPD2: Scoring distribution: 500 — 750 — 1250 — 1500 — 2000 — 2500

UPD3: Editorial

Hello Codeforces!

ssense and I are very glad to invite you to Codeforces Round #726 (Div. 2) which will take place on Jun/18/2021 17:35 (Moscow time). The round will be rated for participants with a rating lower than 2100. Division 1 participants are also welcomed to take part in the competition but it will be unrated for them.

The round was originally planned to be a division 3 round so the problems might be slightly easier than average Div 2.

You will be given 6 problems and 2 hours to solve them.

We would like to thank the following people:

• 1-gon for amazing coordination of our round!

• antontrygubO_o for testing, translating statements and providing useful ideas!

• Maksim1744, Ari, qpwoeirut, magnus.hegdahl, PurpleCrayon, Brodicico, Omkar, DenjellBoone, Arsenie, Lost_Arrow, Etherite, asrinivasan007, nishuz, cringeworthyplayz, Nika_Tamliani, Vpurice for testing and providing invaluable feedback!

• MikeMirzayanov for great Codeforces and Polygon platforms!

• You, for participating!

The scoring distribution is: 500 — 750 — 1000 — 1500 — (1250+1750) — 2000.

UPD: Editorial

Hello everybody!

After a long break I would like to announce the fourth Bioinformatics contest organized by ITMO University, Bioinformatics Institute, Rosalind and Stepik. The contest is sponsored by JetBrains, Yandex, Serokell, and Genotek.

The contest is hosted on Stepik platform. To participate you have to sign the rules.

The contest consists of two rounds:

• The Qualification round is already started today. It will be open until June 19 11:59 UTC+0.
• The Final round will be held for 24 hours starting at June 26 13:00 UTC+0.

The contest is prepared by the following team: Alexey Sergushichev, Nikita Alexeev, Nebuchadnezzar, demon1999, tourist, cdkrot, GShark, doreshnikov (all ITMO University), German Demidov (Center for Genomic Regulation), Andrey Prjibelski (CAB SPbU).

Are there any prizes?

• 1st place – Whole Genome Sequencing
• 2nd and 3rd – Whole Exome Sequencing
• 4th and 5th – 23andMe or Genotek DNA Service
• 1st–30th – Honorable Bioinformatics T-Shirt

Do I need to know biology?

The knowledge of biology is not necessary to solve the problems!

We wish that you will like the problems!

Good luck!

Hello, Codeforces!

Welcome to the Codeforces LATOKEN Round 1 (Div. 1 + Div. 2) supported by LATOKEN, that will start on Jun/13/2021 18:35 (Moscow time). It will be a combined rated round for both divisions (and div 3). Please, note the unusual start time.

All problems were created by Aaeria, crackersamdjam, Dormi, Ninjaclasher, and Plasmatic.

We would like to thank:

• Valentin Preobrazhenskiy from LATOKEN supporting the round.
• 300iq and KAN for coordinating the round and answering our relentless questions.
• arvindr9, Delmos, duality, growup974, m371, PurpleCrayon, rkm62, socho, wleung_bvg, and Zeyu for their invaluable advice and suggestions.
• MikeMirzayanov for great systems Codeforces and Polygon.

You will be given 8 problems and 180 minutes to solve them. This contest features at least one interactive problem, so we recommend reading the guide of interactive problems before the contest.

We hope that statements are short and pretests are strong and that you find the problems interesting! Good luck, have fun, and we wish everyone high ratings!

The scoring distribution will be announced closer to the beginning of the round.

Thanks to LATOKEN, winners will get awesome swag:

• 1st place = MacBook Air M1 + Job offering and Stock Options
• 2nd place = Xiaomi Mi 11 + Job offering and Stock Options
• 3rd place = Xiaomi Mi Notebook Pro 15" Enhanced Edition + Job offering and Stock Options
• 4th-10th place = Job offering and Stock Options + Merchandise Pack
• 11th-55th place = Merchandise Pack

Random 10 participants outside of top-55, who solved at least one problem and participated in rated Codeforces rounds before, will get a t-shirt!

A few words from the LATOKEN team:

We welcome you to the intellectual battle between the best coders from around the world! LATOKEN strives to make trading crypto as easy as having a social media account. We are always looking for the best of the best to join our team. As a result, LATOKEN is currently in Coingecko’s Top 15 with over 600 000 app installs within just one year from its launch and 1m+ users in total. The emerging blockchain based financial systems will open exciting opportunities, because crypto is fully global and mostly independent of conservative banks.

If you want to become a part of something bigger, work remotely with a team of international professionals and change the world, contact our recruiters for internships and employment opportunities in the LATOKEN team. Use our bot or fill out the form below and tell us a little about yourself.

UPD: The scoring distribution is 500 — 1000 — 1250 — 1500 — 2250 — (1750 — 1250) — 3250 — 3500.

UPD: Editorial

Congratulations to the winners:

1. Benq
2. tourist
3. Radewoosh
4. Endagorion
5. ecnerwala
6. heno239
7. peehs_moorhsum
8. gamegame
9. Pyqe
10. maroonrk

The prizes will be distributed in the next few days after we remove cheaters.

Hello, Codeforces!

UPD: Since the round seems a little more complicated than usual after testing, we extended the round length by 15 minutes.

<almost-copy-pasted-part>

Hello! Codeforces Round #725 (Div. 3) will start at Jun/10/2021 17:35 (Moscow time). 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 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round, it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

You will be given 7 problems and 2 hours 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 trusted participants of the third division, you must:

• take part in at least two 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.

The problems for this round were invented by MikeMirzayanov, Supermagzzz and Stepavly.

Thanks to Fly_37, -is-this-fft-, A_Le_K, ALILILILILI-KHAN, ANZ1217, hocky, PhaiCoGiaiQuocGia, Sho, ASIXER, songsinger, OlegZubkov, AlexFetisov, darkkcyan, ivanzuki, kocko, Gassa for help with testing the round.

Thanks to MikeMirzayanov for platforms and coordination of our work. Good luck!

</almost-copy-pasted-part>

UPD: Editorial

Hello Codeforces!

We, the disciples of Omkar (qlf9, Tlatoani, hu_tao, golions, and Omkar's newest disciple, rabaiBomkarBittalBang), have written our third contest: Codeforces Round #724 (Div. 2) — Omkar 3. It will be held on Jun/06/2021 17:35 (Moscow time) and will be rated for users in Division 2 (rating lower than 2100). As usual participants with rating >= 2100 are allowed to compete too, but the contest will be unrated for them.

You will be given 2 hours to solve 6 problems. There may or may not be an interactive problem, so it would behoove you to read the guide for interactive problems. There also may or may not be competitive programming problems, so you should be sure to thoroughly understand everything here.

We would like to thank:

• antontrygubO_o and isaf27 for coordinating this round and helping us improve our problems.

• Our testers, kefaa2, 1-gon, Keshi, czhang2718, HackerMonk, Ari, m371, 2020akadaver, smax, PurpleCrayon, AmShZ, FieryPhoenix, Jellyman102, namanbansal013, I_Love_YrNameCouldBeHere, bWayne, Qualified, kassutta, and Omkar. They were great testers so they definitely deserve the karma that they will surely be begging for in the comments.

• MikeMirzayanov for creating the Codeforces and Polygon platforms.

• Omkar for creating the world and the human race.

The scoring distribution is 500 — 1000 — 1500 — 2000 — 2250 — 2500.

May Omkar be with you!

Update: Thank you for participating in our contest! The editorial is here. We have video editorials for every problem there!

Update:

The winners in official standings:

1. xin_chen

2. adc-s11-sadge

3. conqueror_of_rainboy

4. XOXOX

5. TwTwTwTwT

The winners in unofficial standings:

1. neal

2. Maksim1744

3. dlalswp25

4. hank55663

5. fanache99

Congrats!

Hello Codeforces!

On Jun/04/2021 17:35 (Moscow time) Educational Codeforces Round 110 (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 Roman Roms Glazov, 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!

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

If you love technology, enjoy creating, and looking for an exciting career, Front-end Development might be for you! This time we are looking for talented individuals to launch our new programme with.

We are offering up to a 50% scholarship for our Bachelor’s and Master’s degrees, opening the doors for an exciting career in technology for the most talented people in our network.

Requirements:

1. Diploma and transcript of the highest attained education level
2. Professional fluency in English
3. Your CV

What you will learn:

• Coding up to industry standards
• Accelerated learning
• Master new tech frequency
• Javascript frameworks, CSS preprocessors and methodologies, responsiveness, and also visual design
• And more

Make sure to apply before June 30, 2021, to be eligible for the scholarship and reduced application fee.

Some of the advantages of studying at Harbour.Space:

• We change the way of learning
• We learn by doing
• We are your home

We are always happy to see Codeforces members join the Harbour.Space family. Apply now to learn from the best in the field and kickstart your career!

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.

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

Harbour.Space University

Congratulations to the winners:

Congratulations to the best hackers:

And finally people who were the first to solve each problem:

UPD: Editorial is out

Hi, Codeforces users!

We are announcing ITMO Summer Camp in Competitive Programming that will be held online. On each of the 10 days from June 21 to July 2 (the weekend are the rest days) two-hour lecture and two-hour practice session is going to take place.

Each day one topic is covered, and the practice session is a set of problems of that topic. For lectures we use Zoom, and for practice we use Codeforces. Both will be live, so you can ask questions during the lecture and during the practice, the teacher will help you if you are stuck with your code or didn't get something. The lectures and the problem statements are in English. The school is mostly for Codeforces division 2 and 3 participants. You are required the knowledge of high school math and the ability to code simple programs in C++/Java/Python (or any other language that Codeforces supports, but we are not sure we can help with them).

The main topics are:

• Sorting and Binary Search
• Dynamic Programming
• Graphs, DFS, SCC finding
• Graphs, Shortest paths, BFS, Dijkstra's algorithm
• Strings, Prefix-function, Z-function
• Segment Tree
• RMQ, LCA, Sparse Table

The main topics will be covered for sure, but other topics on the official website can be changed depending on average level of students.

The cost of participation is 245 Euro. ITMO Official Certificate will be given to the participants.

To apply, visit https://schools.itmo.ru/en/school/26/. Application deadline is June, 10, 2021.

If you have any organizational questions (regarding documents, payment, certificates, etc) ask the school manager Ekaterina Rassolenko by emailing to e.rassolenko (at) itmo.ru.

UPD: Most probably there will be two learning groups, at different times of day. Current plan is: Morning classes are held from 11:00 to 15:00, evening classes – from 17:00 to 21:00 (GMT +3).

Hi Codeforces!

We are DELTIX. Founded in 2005, DELTIX is one of the market leaders in software development for financial research and products for systematic and algorithmic trading. In 2020 DELTIX joined the EPAM family. Our mission is to turn promising ideas into breakthrough products fast.

We are experts in:

• aggregation, storage, and processing large volumes of time-series data
• data modeling
• testing and deployment of quantitative models

In our team we value skills like:

• knowledge of algorithms
• high-performance coding
• low latency data streams processing

Learn more about DELTIX

Throughout the year, once per quarter, we will be inviting you to join DELTIX rounds at Codeforces. Today, we are excited to welcome you to the first installment of our rounds (joined Div1 и Div2) — Deltix Round, Spring 2021 (open for everyone, rated, Div. 1 + Div. 2), that will start on May/30/2021 17:35 (Moscow time).

It is an open and rated round for both divisions.

We have prepared the following trophies for you:

• 1st place = the most desired console of 2021 — PlayStation 5!
• 2nd place = Nintendo Switch
• 3rd place = Nintendo Switch Lite
• 1-100: branded t-shirts

Another 100 t-shirts will be distributed randomly between 100 participants outside of top-100 and who have solved at least one problem and participated in rated Codeforces rounds before.

Problems have been prepared by our employees: Vladik, netman, AleXman111 and sdryapko.

We would like to say a word of appreciation:

• to KAN and Nebuchadnezzar for coordinating the round
• 74TrAkToR for the idea for one of the tasks, as well as its preparation
• to all testers: kefaa2, Tlatoani, gepardo, andrew, generic_placeholder_name, ajit, 221, PurpleCrayon, 4llower, namanbansal013, growup974, m371, vineet16, rkm62 and viktoria.0907
• and of course, to MikeMirzayanov for Codeforces and Polygon

We will offer participants 8 problems and 135 minutes to solve them. We wish everybody good luck and high ratings!

Fill out a short contact form if you are interested in internship and/or employment opportunities or would like to speak with recruiters or members of our team.

UPD: The scoring distribution is 500 — 1000 — 1500 — 2250 — 2250 — 3000 — 3250 — 3250.

Thank you all for participating! (editorial)

Congratulations to the winners:
1. tourist
2. Radewoosh
3. Um_nik
4. maroonrk
5. ecnerwala
6. jiangly
7. SSRS_
8. Petr
9. scott_wu
10. Maksim1744

We would like to express our special congratulations to the top three leaders! We will try to send you your well-deserved prizes as soon as possible :) Unfortunately, we can not list the people who received 100 random T-shirts due to the fact that the search for cheaters is not completed.