Hello Codeforces!

Sorry for a bit delayed English announcement, we are glad to invite you all to Codeforces Round 744 (Div. 3), third division round held on Sep/28/2021 17:35 (Moscow time). This round was prepared by me and MikeMirzayanov and we hope that you'll find the problems interesting and enjoy solving them.

I would like to thank MikeMirzayanov for helping me with both writing and preparing the problems for this round. Since it's the second Div. 3 round held I'm involved in but only the first one I'm preparing problems for from zero all the way to the end, without his guidance it would've taken much more of my time.

Also special thanks to nizamoff, andreumat, QAZZY, Vladosiya, CtrlAlt, vladmart, Igorjan94, okwedook, ashmelev and Aris for testing the round and giving their feedback on the problems as well as to Gassa and geranazavr555 for proofreading and correcting the statements. This round is very noticeably better than it could've been without your contribution. And last but not least, thanks to everyone who'll be participating! This round contains 7 to 8 problems and is expected to be of decent level of difficulty 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 ACM-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. We tried to make tests strong enough but it doesn't at all guarantee that open hacks phase will be pointless.

You will be given 7-8 problems and 2 hours 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 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.

Good luck and have fun!

UPD: Editorial is out!

Hello Codeforces!

On Sep/20/2021 17:35 (Moscow time) Educational Codeforces Round 114 (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, Roman Roms Glazov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD: Editorial is out

Hello.

Sorry for it. Actually, right now I don't have any idea why testing is so slow now. Obviously, it doesn't work as expected. It is not because of problems. So please don't blame writers or coordinators. I'm investigating the reason, but don't see it now.

I myself am very upset and I apologize to the authors, coordinator, and participants. I will do my best to find the cause and fix it. Surprisingly, we haven't made any big changes to this part of the system lately. But something went wrong.

Mike.

UPD: https://codeforces.com/blog/entry/95081#comment-841873

Hello Codeforces!

Asymmetry and I are glad to invite you to Codeforces Round 743 (Div. 1) and Codeforces Round 743 (Div. 2), which will be held on Sep/18/2021 17:35 (Moscow time).

Each division will have 6 problems and 2 hours to solve them. All problems were written and prepared by Asymmetry and me. The round will be rated for both divisions.

We would like to thank:

• Monogon for coordinating the round and helping us with the problems.
• mnbvmar, gamegame, dorijanlendvaj, tnowak, Jasiekstrz, ijxjdjd, phattd, lcaonmst, -_-INV4D3R-_-, ToxicPie9, Shinchan01 and Krzaq for testing the round and providing useful feedback.
• ToxicPie9 for being a VIP tester.
• finally, MikeMirzayanov for great platforms Codeforces and Polygon!

We've put great efforts into preparing this round and we hope that you will enjoy it.

Good luck!

UPD: We would also like to thank Ari for testing the round and KAN for translating the statements into Russian.

UPD2: Here are the scoring distributions:

Div. 1: $$$500$$$ — $$$1250$$$ — $$$1750$$$ — $$$2500$$$ — $$$2500$$$ — $$$3250$$$

Div. 2: $$$500$$$ — $$$1000$$$ — $$$1500$$$ — $$$2250$$$ — $$$2750$$$ — $$$3500$$$

UPD3: We are sorry that the round became unrated due to the long queue. We hope that you enjoyed the problems anyway.

Winners

Congratulations to the winners!

Div1.

1. tourist

2. Benq

3. VivaciousAubergine

4. ecnerwala

5. Molewus

Div2.

1. ChenRui

2. rainboy

3. OguriCap

4. _October

5. Dallby

UPD4: Editorial is out!

Hello, Codeforces!

On 12.09.2021 17:35 (Московское время) we will host Codeforces Global Round 16.

It is the fourth round of a 2021 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 2021:

• 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 2021 supported the global rounds initiative!

The problems were written and prepared by shishyando and Artyom123.

We would like to thank these people:

• isaf27, the one who did a lot of things for the round to happen
• Shinchan01, Absyarka, Ziware, ijxjdjd, wxhtzdy, Kotehok3, ptd,physics0523, Igorbunov, kpw29, Kirill22, Monogon, pashka for testing
• Kirill22 for submitting many different solutions
• Monogon for being a VIP tester and his hilarious greetings in russian
• kpw29 for spending much time discussing the problems with me
• physics0523 for making researches about the tasks (as he always does)
• MikeMirzayanov for Codeforces and Polygon platforms and for his immeasurable contribution to the development of the community!

You will have 2.5 hours to solve 8 problems. As always, we highly recommend reading all problems. Moreover, we really hope you upsolve the problems after the round, there are some interesting things to find out!

One of these problems is interactive, please see the guide of interactive problems if you are not familiar with it.

Score Distribution:

500 — 750 — 1000 — (750 + 1000) — 2000 — 2500 — 3000 — 3750

Editorial:

The editorial

Winners

System testing finished, congrats to the winners!

1. Radewoosh
2. tourist
3. QAQAutoMaton
4. jiangly
5. ksun48
6. Alice_foo_foo
7. He_Ren
8. Benq
9. tatyam
10. hitonanode

Hello Codeforces!

On Sep/08/2021 17:35 (Moscow time) Educational Codeforces Round 113 (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!

Congratulations to the winners:

69 ^nice successful hacks and 304 unsuccessful hacks were made in total!

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

UPD: Editorial is out

Hello Codeforces!

I am in the process of making improvements and updates to the judgment machines. I've read the post https://codeforces.com/blog/entry/94587 and I think, maybe it is a good idea to make such a compilation line -O3 -funroll-loops -march=native -mtune=native? I haven't done any research that it is definitely better than -O2 and it is best in the general case for CP solutions. In a way, this will only strengthen the gap from Python/PyPy/Java, on the other hand: in pragmas and so you can set up everything. What do you think? What are suggestions to the command line?

P.S. You got it right. Yes, gcc11 std=c++20, pypy3 64-bit and more are coming.

Hey there Codeforces!

flamestorm and I are glad to invite you to our first-ever Codeforces round, Codeforces Round 742 (Div. 2), which will be held on Sep/05/2021 17:35 (Moscow time). This round will be rated for participants with rating lower than 2100.

Special shoutouts to:

• adedalic, for his fantastic coordination and translation of the round!

• MikeMirzayanov, for creating the amazing Codeforces and Polygon platforms!

• dorijanlendvaj, awoo, YouKn0wWho, PurpleCrayon, phattd, ijxjdjd, stefdasca, tenth, Aaeria, Eyed, kalki411, Shinchan01, BRCode, namanbansal013, Urvuk3, mudkip, richy6, and tdpencil for testing the round, catching any mistakes and providing lots of valuable feedback! We tried to get a large range of testers with different coding experiences so that everybody enjoys the round.

• stefdasca once again, for creating video editorials which will be available after the contest!

• saarang, not because he contributed anything to the round, but because he would annoy me for months if I didn't mention him here.

• And you, the user, for upvoting this blog and giving me contribution participating in this contest!

You will have 2 hours to work on (and solve!) 6 problems. At most one of the problems will be interactive. Make sure to read this blog and familiarize yourself with these types of problems before the round! You are highly encouraged to read all the problems ;).

UPD: The score distribution is 500 — 1000 — 1500 — 1750 — 2250 — 2750.

Good luck, and see you on the scoreboard!

UPD: Editorial is out!

UPD: Congrats to the winners!

Div. 2 (the only 5 contestants to solve the whole set!):

1. shengtongtong

2. zihouzhong

3. NOOB228

4. definition_win

5. TearsFreeze

Div. 1 + 2:

1. SSRS_

2. dlalswp25

3. LayCurse

4. neal

5. Vercingetorix

We hope you enjoyed the round. See you soon!

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 such skills as:

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

We are excited to announce that one of our products TimeBase Community Edition joined a FinTech Open-Source Foundation (FINOS) on the 14th of July.

TimeBase is a multi-faceted, open-source data-streaming powerhouse, combining a time-series database, message broker, data modeling, and a well-optimized serialization framework. Originally, TimeBase was designed to address use cases in the financial domain. Nevertheless, we take on new challenges in other areas such as IoT, cloud computing, clustering, high-performance computing, parallel data processing, and Big Data to name a few.

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 second installment of our rounds (joined Div. 1 and Div. 2) — Deltix Round, Summer 2021 (open for everyone, rated, Div. 1 + Div. 2), that will start on Aug/29/2021 17:35 (Moscow time).

It is an open and rated round for both divisions.

We have prepared the following trophies for you:

• 1st place = MacBook Air
• 2nd place = iPad Pro
• 3rd place = iPad Air
• 1-100 = branded t-shirts

Another 100 t-shirts will be distributed randomly between participants outside the top-100 but within the top-1000 and who participated in rated Codeforces rounds before.

All problems, except the last one, have been prepared by members of our team: Vladik, netman and AleXman111.

We would like to say a word of appreciation to:

• KAN and budalnik for the round management.
• 300iq for creating a great problem that has naturally fitted in our set of problems for this round.
• to all testers: antontrygubO_o, 244mhq, andrew, Mediocrity, Vaseline_Warrior, g1phy, nweeks, ptd, phattd, dmitriyklebanov, Alladdin, wxhtzdy, Shinchan01, Fasys and sovspace.
• MikeMirzayanov for Codeforces and Polygon systems.

We will offer participants 8 problems and 150 minutes to solve them. We wish everybody good luck and high ratings!

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

UPD: After processing all testers' feedback, we decided to extend the competition by 15 minutes. The total duration is 150 minutes.

UPD2: The scoring distribution is 500 — 1000 — 1500 — 1500 — 2000 — 2500 — 3000 — 3500. Note the equal complexity of C and D.

Thank you all for participating! (editorial)

Congratulations to the winners:
1. Rewinding
2. jiangly
3. Benq
4. Egor
5. TLE
6. ainta
7. Radewoosh
8. Golovanov399
9. ecnerwala
10. maroonrk