Hello, Codeforces!

On Sep/12/2021 17:35 (Moscow time) 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 shishin 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, m371, Kotehok3, 221,physics0523, Igorbunov, kpw29, Kirill22, 1-gon, pashka for testing
• Kirill22 for submitting many different solutions
• 1-gon 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, shxgun, ijxjdjd, stefdasca, epicxtroll, Aaeria, Eyed, rkm62, Shinchan01, BRCode, namanbansal013, Urvuk3, 1_2_oatmeal, 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!

• saarang123, 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. snuphy

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 Nebuchadnezzar 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, kefaa2, andrew, Fedosik, Vaseline_Warrior, g1phy, nweeks, 221, shxgun, dmitriyklebanov, Alladdin, m371, 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. Miracle03
2. jiangly
3. Benq
4. Egor
5. TLE
6. ainta
7. Radewoosh
8. Golovanov399
9. ecnerwala
10. maroonrk

Choose the way, five paths there for you to find
Turn the page, the question lies between the lines...

Hello, Codeforces!

I hoped that once there will be my second round, and finally, here it is!

I am very glad to invite you to the Codeforces Round #741 (Div. 2), which will take place in Aug/26/2021 17:35 (Moscow time). This round will be rated for the participants with rating lower than 100000110100 (2100).

My thanks to:

• antontrygubO_o for rejecting problems A his great coordination of this round! Thanks!

• gepardo made a lot. There wouldn't have been this contest if he didn't help me. Thanks!

• EIK this is the person who taught me competitive programming — my Informatics teacher. Thanks!

• MikeMirzayanov for Codeforces and Polygon platforms. Thanks!

• You for participating in this round. Thanks!

You will have 2 hours and 15 minutes for solving 6 tasks, one of which will be divided into easy and hard verions.

One of the problems will be interactive. So, it is recommended to read the ultimate guide on your favourite type of problems before the round.

I hope you will enjoy the round!

Round testers: kefaa2, BigBag, DreamingLeaf, Kuroni, programmer228, hu_tao, Vladik, bWayne, kassutta, asrinivasan007.

Score distribution: 500-1000-1250-(1250+1250)-2750-3500.

UPD: It was decided to add a sixth task to the round to balance the difficulty.

UPD2: Editorial is here!

UPD3: Congratulations to the winners!

Hello again!

VK Cup 2021 - Final (Engine) starts very soon: on Aug/22/2021 15:05 (Moscow time). Today, 32 best contestants of the elimination round will be fighting for cash prizes and eternal glory.

You can follow the course of the contest and root for your favorite contestants via this link.

Everyone except for VK Cup 2021 finalists is invited to Codeforces Round #740 (Div. 1, based on VK Cup 2021 - Final (Engine)) and Codeforces Round #740 (Div. 2, based on VK Cup 2021 - Final (Engine)) that start a couple of days later: on Aug/24/2021 17:35 (Moscow time). The rounds will be rated for everyone.

All the problems were authored and prepared by me. Big thanks to everyone without whom this round would not be possible: KAN, PavelKunyavskiy, scott_wu, xiaowuc1, 1-gon, Aleks5d, lperovskaya, MikeMirzayanov. Special thanks to s-quark (2nd place of the first ever VK Cup 2012!) for inspiring problem titles.

You will be given 6 problems and 2 hours 30 minutes to solve them in both divisions. It is recommended to read all the problems. Good luck!

UPD: Scoring distribution in the VK Cup finals: 500 — 1250 — 1500 — 2000 — 3000 — 3500

UPD2: Congratulations to the winners of the VK Cup 2021 Final Round!

1. never_giveup
2. Maksim1744
3. Um_nik
4. SpyCheese
5. Nebuchadnezzar
6. vepifanov
7. Golovanov399

UPD3: Division 1 round will be held on the VK Cup 2021 Finals problem set without any changes.

Scoring distribution for Div. 1: 500 — 1250 — 1500 — 2000 — 3000 — 3500

In Division 2 problems BDEF will match problems ABCD of Div. 1. Problems A and C of Div. 2 will be similar to problems F and E of Div. 1 (albeit being much easier). Besides that, problem D of Div. 2 will have a subtask with lower constraints than the original problem.

Scoring distribution for Div. 2: 500 — 1250 — 1250 — (1500 + 1000) — 2500 — 3500

As a reminder, the standings of the VK Cup Finals are available via this link — feel free to try gaining an advantage using all the information available before the round :)

UPD4: Editorial is available.

Hello, Codeforces.

I and DK318 joined the Codeforces team in June. These three months we mainly dealt with the development of the Polygon platform. In this post, we would like to present to you a list of what we have done during this time. Most of the changes were made to attain easier problem creation. This list does not include minor bug fixes or any improvements that are invisible to users.

Tables support when rendering statements in HTML

Now it's possible to insert the most basic tables in your HTML statements. For example, you can show the scoring system of your problem or insert several images side by side. Only column text alignment and border specification are supported now.

A brief manual for writing statements

We bet a lot of users who wrote statements were confused by the fact that a lot of TeX commands are not working when rendering in HTML. Now you can access the manual on the statements page to learn about supported commands with examples as well as other tips for writing better statements.

You can check out the manual here.

Reworked how one can add problems into a contest

We completely reworked the way you add problems on the contest page. You can select the problems from the list of accessible problems: they will be added to a separate list. You can also filter your problems so you can find the needed one much quicker. We performed some optimizations as well so even if you have thousands of accessible problems, this page will lag much less.

Hello, Codeforces!

I'm glad to invite you to amazing (we've tried to make it such) Codeforces Round #739 (Div. 3) which will start on Aug/18/2021 17:35 (Moscow time). This round is my (MrPaul_TUser) second round a significant contribution to which was also made by MikeMirzayanov, BledDest, DK318, unreal.eugene, and geranazavr555.

The round contains 7-8 problems. The difficulties of the problems are expected 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 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 really strong tests — just like you will be surprised if many solutions fail after the contest is over.

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.

Thanks to powergee101, artsin666, WitchOfTruth, ivanzuki, A_Killer, mahade31, I_Remember_Olya_ashmelev, nooinenoojno, Gassa, _c_k_r_, spotless, iankury, UpS0lver, ncduy0303, and Vladosiya for testing the round and improving tasks.

Good luck and have fun!

UPD Editorial

Hi Codeforces!

We are glad to invite you to our first Codeforces Round Codeforces Round #738 (Div. 2) which will be held on Aug/15/2021 17:35 (Moscow time). This round will be rated for participants with rating less than 2100. We will be glad to see participants from the first division to join out of competition as well!

In this round, as the best friend of Mocha's, you are going to help her to solve the problems she meets.

The problems are prepared by 2sozx, JJLeo, Serval, CalvinJin and me. We hope you will enjoy the round. :P

We would like to thank:

• 1-gon for awesome coordination of this round and helping us improve our problems.

• Toxel for excellent testing and discussion of this round.

• cppascalinux, PurpleCrayon, ijxjdjd, m371, qxforever, fixed_lxy, HKvv, jxm2001, GGN_2015, I-AK-ACM, wzy2001wzy, xrbxbn, BH18376359, zhtjtcz, lgwza, qwertyczx, godel_bach, withinlover, Saisyc, Matrix53, rancy, asrinivasan007, QuangBuiYT, lcj_rating1600, Atlantis592, shakugan_no_shanatan_, DovahkiinGA and 5095187020216 for testing our rounds

• MikeMirzayanov for the amazing Codeforces and Polygon platforms.

You will be given 5 problems to solve in 2 hours.

Scoring distribution: 500—750—1000—(1500—1500)—3000.

We recommend you to read the statements of all problems. Good luck & Have fun! :D

UPD: Great thanks to KAN and isaf27 for helping with Russian language translation and clarifications.

UPD2: Sorry for the long queue and my mistake in estimating the difficulty of problem D2 and E.

UPD3: Editorial is available now.

UPD4: Thank you for your participation in this round! Congratulations to the winners!

Div. 2

1. Suckmycode
2. Wlxsohandsome
3. idontwannawin
4. shu_ya_zi
5. _Kubic_

Div. 1 + Div. 2

1. neal
2. ksun48
3. Geothermal
4. sjc061031
5. Kirill22