Codeforces Global Round 13 Hello Codeforces! On [contest_time:1491] we will host [contest:1491]. **<img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width: 200.0px;float: right;margin: 0 1.0em 1.0em 1.0em;max-width: 100.0%;max-height: 100.0%;">** It is the first round of a 2021 series of [Codeforces Global Rounds](https://mirror.codeforces.com/blog/entry/65002). 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](https://pastebin.com/QT5sXEaT). - 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 ...

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Codeforces LATOKEN Round 1 (Div. 1 + Div. 2) Hello, Codeforces! Welcome to the [contest:1534] supported by LATOKEN, that will start on [contest_time:1534]. It will be a combined rated round for both divisions (and div 3). **Please, note the unusual start time.** All problems were created by [user:Aaeria,2021-06-09], [user:crackersamdjam,2021-06-12], [user:Dormi,2021-06-09], [user:Ninjaclasher,2021-06-09], and [user:Plasmatic,2021-06-09]. We would like to thank: - Valentin Preobrazhenskiy from LATOKEN supporting the round. - [user:300iq,2021-06-10] and [user:kan,2021-06-10] for coordinating the round and answering our relentless questions. - [user:arvindr9,2021-06-09], [user:delmos,2021-06-09], [user:duality,2021-06-09], [user:growup974,2021-06-09], [user:m371,2021-06-09], [user:purplecrayon,2021-06-09], [user:rkm62,2021-06-09], [user:socho,2021-06-09], [user:wleung_bvg,2021-06-09], and [user:zeyu,2021-06-09] for their invaluable advice and suggestions. - [user:MikeMirzayanov,2021-06-09] for great systems Codeforces...

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Codeforces Global Round 30 Hello, Codeforces! We are pleased to announce the resumption of the Global Rounds. Thanks to XTX Markets for supporting the initiative! In 2025, we will hold 3 such rounds. The series results will take into account the best 2 participations out of 3. On [contest_time:2164] we will host [contest:2164]. **<img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width: 200.0px;float: right;margin: 0 1.0em 1.0em 1.0em;max-width: 100.0%;max-height: 100.0%;">** Codeforces Global Round 30 marks the second round in the 2025 series of Codeforces Global Rounds. These rounds are open and rated for everyone. The prizes for this round are as follows: - The top 30 participants will receive a t-shirt. - 20 t-shirts will be randomly distributed among participants ranked between 31 and 500, inclusive. The prizes for the 3-round series in 2025: - In each round, the top-100 participants get points according to the [table](https://pastebin.com/NMzrRc...

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Codeforces Global Round 13 Editorial [problem:1491A] ------------------ Setter: [user:syksykCCC,2021-02-28] Prepared by: [user:syksykCCC,2021-02-28] <spoiler summary="Hint 1"> How can we find the largest $k$ such that the $k$-th smallest element of the array is $0$? </spoiler> <spoiler summary="Hint 2"> How can we maintain $k$? </spoiler> <spoiler summary="Solution"> Let's define $cnt$ to represent the number of 1s in the array. For the modifications, if $a_i$ is already $1$ now, then we let $cnt \gets cnt - 1$. Otherwise, let $cnt \gets cnt + 1$. For the querys, just compare $cnt$ with $k$. If $cnt \ge k$, the answer will be $1$. Otherwise, the answer will be $0$. The complexity : $O(n + q)$. </spoiler> <spoiler summary="Code (C++)"> ```c++ #include <bits/stdc++.h> using namespace std; const int N = 1e6 + 5; int n, q, a[N], cnt; int main() { scanf("%d%d",&n,&q); for(int i = 1; i <= n; ++i) { scanf("%d",a+i); cnt += a[i]; } while(q--) { int opt, x; ...

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Wrapping up the Global Rounds 2025 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width: 240.0px;float: right;margin: 0 1.0em 1.0em 1.0em;max-width: 100.0%;max-height: 100.0%;"> Hello Codeforces, As 2025 comes to an end, it is time to start summing up the results. This post is about the Global Rounds. Since September, we have held a series of three Global Rounds, numbered from 29 to 31. This is the perfect moment to once again express our gratitude to XTX Markets for their initiative in organizing these rounds and their constant support over the years. Such stability in supporting the competitive programming movement is truly admirable and highly appreciated by the community. I wish XTX Markets a fantastic 2026, full of success and victories! In each of the three rounds, 50 t-shirts were awarded (to the top 30 participants and 20 random participants ranked between 31st and 500th). This year, we had to change the manufacturing and shipping process, so it is still a work...

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Squarepoint Challenge (Codeforces Round 1055, Div. 1 + Div. 2) Annyeonghaseyo, Codeforces! We invite you to participate in [contest:2152], which will be held on [contest_time:2152]. The round will be **rated for everyone**. You will be given **8 problems**, one of which is divided into two subtasks, and **3 hours** to solve them. One of the problems will be interactive, so make sure to read the [guide for interactive problems](https://mirror.codeforces.com/blog/entry/45307) before the contest. The problems are authored and prepared by [user:as_dfsdf,2025-09-29], [user:djm03178,2025-09-29], [user:ko_osaga,2025-09-29], and [user:qwerasdfzxcl,2025-09-29]. We would like to thank: - [user:errorgorn,2025-09-29] for great coordination. - [user:Alexdat2000,2025-09-29] for great Russian translation. - [user:Adam_GS,2025-09-29], [user:ainta,2025-09-29], [user:bangan,2025-09-29], [user:BuzzyBeez,2025-09-29], [user:cookiedoth,2025-09-29], [user:Dragos,2025-09-29], [user:gamegame,2025-09-29], [user:garam1732,2025-09-29], [user:Geothermal,2025-09-29],...

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Codeforces Global Round 25 Editorial Hi, we hope you enjoyed our problems! For the playlist of songs used in the problem statements, click [this link](https://www.youtube.com/playlist?list=PLTVdHvnX6LZhAJre49E7M7tpGA30WlBM3). [problem:1951A] Author: [user:MofK,2024-04-06] <br> Prepared by [user:Kuroni,2024-04-06] <br> First solve: [user:xiachong,2024-04-06] at 00:01 <spoiler summary="Tutorial and Implementation"> [tutorial:1951A] [submission:255371605] </spoiler> <spoiler summary="Rate this problem"> Yay Meh Nay Banger song </spoiler> [problem:1951B] Author: [user:MofK,2024-04-06] <br> Prepared by [user:Kuroni,2024-04-06] <br> First solve: [user:pavement,2024-04-06] at 00:05 <spoiler summary="Hint 1"> What is the condition for your cow to win her first match? </spoiler> <spoiler summary="Hint 2"> If your cow is not already winning her first match, there are at most two candidate positions you can swap her to. </spoiler> <s...

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What if tourist goes rainboy mode? (Simulation) DISCLAIMER: NO TOURISTS AND RAINBOYS WERE PINGED Ah yes, two names that most people on Codeforces have heard -- <b>t<span style="color:red;">ourist</span></b> and <b><span style="color:purple;">rainboy</span></b>, one known as the CP Legend, and one as the user who does everything reverse. Such a great idea to put them together &mdash; a hypothetical user with the same ability as <b>t<span style="color:red;">ourist</span></b>, and solves problems the <b><span style="color:purple;">rainboy</span></b> way. _For those unaware of the "rainboy way", it means solving the problems in reverse order. In particular, if he cannot solve the final problem, he solves no problems in the contest._ Unfortunately, <b><span style="color:purple;">rainboy</span></b> had not yet reached red, peaking at 2398 rating. How far can this user go? We shall simulate this user through all the contests that tourist and rainboy took part in comparably, which adds up to 60 contests from [contest:745] to [cont...

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Problems that I authored so far **UPD 1 [May 17 2025]:** I added my problems from Ukrainian Olympiad in Informatics (among others). They are available here: [contest:105820] Hi everyone! I wanted to write such a blog for a long time, motivated by similar blogs [by](https://mirror.codeforces.com/blog/entry/108940) [user:adamant,2023-02-20] and [by](https://mirror.codeforces.com/blog/entry/108595) [user:tibinyte,2023-02-20]; I finally decided to do it after my Universal Cup contest. This is not a super-comprehensive list, I also set some problems for some local contests, but that's most of it. I want to encourage other setters to write such blogs. For me, it's very interesting to read about the backstories of some problems and also to see all the problems by some author gathered in one place (as most authors give problems to several platforms). One important point. As you will see from the comments, many of my problems were improved by other people, and I myself improved some problems by other people. I think that it's cruc...

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Codeforces Global Rounds 2020: Final Results In 2020, with the support of XTX Markets, 6 rounds of the Codeforces Global Rounds were held. Each round was common for both divisions. All such rounds were rated for all participants. At each such round, 50 brand T-shirts were handed out, and we gave T-shirts to all problem writers! I say a big thank you to XTX Markets (and personally to Yuri Bedny and Alexander Gerko) for supporting Global Rounds. Without your help, we could not host them! I sincerely admire companies like these who come to support and develop the community that some of their employees come from. It will be great if other companies follow the example and also offer their help. We need it! The prizes for the 6-round series in 2020: - In each round, top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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...

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Invitation to CodeChef October Cook-Off 2020 Hi! I am thrilled to invite you to participate in CodeChef’s [October Cook-Off](http://bit.ly/COOK123-Codeforces), this Sunday, October $18$, from [9:30 pm to 12:00 am IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=October+Cook-Off+2020&iso=20201018T2130&p1=44&ah=2&am=30). Followings are the basic information: - Participants in each division will be given $6$ problems and $2.5$ hours to solve them. - All problems have been cooked by me. - Statements are very short unlike this announcement! - Problems will have strong samples. - There will be an interactive problem in this round, so, you should know how to [deal with them](https://discuss.codechef.com/t/interactive-problems-and-the-way-to-deal-with-them/21185). - I hope your internet connection is good as some of the problems will feature awesome animations that I have created using Manim! Yeah, it means the problems will have better explanations. - In my [last contest](https://www.codechef.com/COOK120?it...

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Educational Codeforces Round 88 [Rated for Div. 2] Hello Codeforces! On [contest_time:1359] [contest:1359] will start. Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>. 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 [user:Roms,2020-05-27] Glazov, Adilbek [user:adedalic,2020-05-27] Dalabaev, Vladimir [user:vovuh,2020-05-27] Petrov, Ivan [us...

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Codeforces Global Rounds 2022: Final Results (GR19-GR24) Hello, Codeforces. It's time to take stock of last year. Shall we begin? And we are happy to sum up the results of the last season of Global Rounds. We announce the results! We remind you that the global rounds are a joint initiative of XTX and Codeforces. We hold 6 such rounds per year. All of them are open to both divisions. At each such round, 50 brand T-shirts were handed out, and we are happy to give T-shirts to all problem authors. The prizes for the 6-round series are: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. [cut] The final standings after six rounds (sorted by total points in four best-placed rounds): | Place | Contestant | = | GR 19 | GR 20 | GR 21 | GR 22 | GR 23 | GR 24| |--|--|--|--|...

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Codeforces Global Rounds 2019: Final Results In 2019, with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds were held. Each round was common for both divisions and had 7–9 problems. The duration of the rounds was 2-3 hours, depending on the number and complexity of the problems. All such rounds were rated for all participants. At each such round, 50 brand T-shirts were handed out, and we gave T-shirts to all authors and problem testers as well. The prizes for the 6-round series in 2019: - In each round, top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. Final results: [cut]<br/> | Place | Contestant | = | Round 1 | Round 2| Round 3 | Round 4 | Round 5 | Round 6 | | - | - | - | - | - | - | - | - | - | | 1 | [user:tourist,2019-12-17] | <b> 2987 </b> | ...

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Top 50 Voted Blog Posts in 2021 Hi. Here is the list of top-voted blog posts in 2021. Find something interesting for yourself? | # | Post | Votes | Author | | - | - | - | - | | 1 |<a href="/blog/entry/95106">The Ultimate Topic List (with Resources, Problems and Templates)</a> | 4383 | [user:YouKn0wWho,2022-01-02] | | 2 |<a href="/blog/entry/96333">Codeforces Round #752</a> | 3156 | [user:YouKn0wWho,2022-01-02] | | 3 |<a href="/blog/entry/87882">User activity in the profile! [new, Feb. 2021]</a> | 3055 | [user:geranazavr555,2022-01-02] | | 4 |<a href="/blog/entry/89227">Codeforces Round #712</a> | 2866 | [user:Monogon,2022-01-02] ...

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8VC Venture Cup Announcement <img src="http://assets.codeforces.com/images/8vc/8vc-venturecup-logo.png" style="float:right;margin:0 1em 1em 1em"/> Hey Codeforces! I’ve worked with Addepar and the broader 8 | family of companies in Silicon Valley throughout 2014 and 2015, and it’s been an excellent experience. I would encourage everyone in the community to learn more about the great work that these companies are doing and I’m happy to announce that 8 | Partners will be hosting the 8 | VC VentureCup on Codeforces! It’ll be a fun contest and I’ve worked on the problems along with a few competitive programmers in our network. The contest will begin on February 13 and consist of two rounds. ##### ABOUT 8 | PARTNERS <a href="http://eight.vc/">8 | Partners</a>, which consists of Joe Lonsdale (co-founder of Palantir) and his core team from Formation | 8, is a Silicon Valley venture capital firm that invests in industry-transforming technology companies. The team's investment portfolio includes companies suc...

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Codeforces Global Rounds 2021: Final Results (GR13-GR18) Tomorrow will be the first global round of this year. And we are happy to sum up the results of last season. We announce the results! We remind you that the global rounds are a joint initiative of XTX and Codeforces. We are happy to announce that they continue into the new year. We hold 6 such rounds per year. All of them are open to both divisions. At each such round, 50 brand T-shirts were handed out, and we are happy to give T-shirts to all problem authors. The prizes for the 6-round series are: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. The final standings after six rounds (sorted by total points in four best placed rounds): | Place | Contestant | = | GR 13 | GR 14 | GR 15 | GR 16 | GR 17 | GR 18| |--...

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Contests hack statistics (Number of hacks by round) Just felt like gathering some data about hacks. Parsed around ~400 last contests Probably it would be worth it to also include SFT, but whatever Educational 96 is not finished yet but also whatever Last 100 ------------------ **847** Educational Codeforces Round 96 (Rated for Div. 2) **30** Codeforces Global Round 11 **248** Codeforces Round #674 (Div. 3) **0** 2020 ICPC, COMPFEST 12, Indonesia Multi-Provincial Contest (Unrated, Online Mirror, ICPC Rules, Teams Preferred) **97** Bubble Cup 13 &mdash; Finals [Online Mirror, unrated, Div. 2] **86** Bubble Cup 13 &mdash; Finals [Online Mirror, unrated, Div. 1] **20** Codeforces Round #675 (Div. 2) **1** Codeforces Round #672 (Div. 2) **70** Codeforces Round #671 (Div. 2) **58** Educational Codeforces Round 95 (Rated for Div. 2) **3** Codeforces Round #673 (Div. 2) **11** Codeforces Round #673 (Div. 1) **73** Codeforces Round #667 (Div. 3) **121** Grakn Forces 2020 **4** Co...

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Codeforces Global Rounds 2019: Current Results After Four Rounds In 2019, with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds will be held. These will be common rounds for both divisions of 7–9 problems each. The duration of the rounds will be 2-3 hours, depending on the number and complexity of the problems. All such rounds will be rated for all participants. <i>At each such round, 50 brand T-shirts will be handed out, and we will be happy to give T-shirts to all authors and problem testers.</i> The prizes for the 6-round series in 2019: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. Current standings after four rounds: | Place | Contestant | = | Round 1 | Round 2| Round 3 | Round 4 | | - | - | - | - | - | - | - | | 1 | [user:tourist,2019-07-21] | 241...

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Educational Codeforces Round 143 [Rated for Div. 2] Hello Codeforces! On [contest_time:1795] [contest:1795] will start. Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>. 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 [user:adedalic,2023-02-15] Dalabaev, Vladimir [user:vovuh,2023-02-15] Petrov, Ivan [user:BledDest,2023-02-15] Androsov, Ma...

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Invitation to IndiaHacks 2nd Elimination 2017 On [Sunday, August 6th, 22:00 IST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20170806T22&p1=438&ah=3), we will hold the 2nd elimination for IndiaHacks (some more details [here](http://mirror.codeforces.com/blog/entry/52069)). The top 900 individuals who qualified through previous rounds will have the opportunity to participate in this round. The top 25 global participants and top 25 Indian participants will advance to the final round. The link to the contest is [here](https://www.hackerearth.com/challenge/competitive/indiahacks-2017-programming-wave-20-eliminator/). After the official round is over, the next morning, on [Monday, August 7th, 11:35 IST](https://www.timeanddate.com/worldclock/fixedtime.html?day=7&month=8&year=2017&hour=9&min=5&sec=0&p1=166), we'll hold an unofficial unrated mirror here on Codeforces. This mirror will have ICPC rules. For participants of the official round, please hold off on discussing the problems publicly until after this mirror is over. ...

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Codeforces Global Rounds 2021: Current Results (GR13-GR17) In 2021 (as in 2019 and 2020), with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds are held: common rounds for both divisions of 7–9 problems each. The duration of the rounds is 2-3 hours, depending on the number and complexity of the problems. All such rounds are rated for all participants. <i>At each such round, 50 brand T-shirts are handed out, and we are happy to give T-shirts to all problem authors.</i> The prizes for the 6-round series in 2021: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - The final result for each participant is equal to the sum of points he gets in the five rounds he placed the highest. - The best 20 participants over all series get sweatshirts and place certificates. Current standings after five rounds (sorted by total points in four best placed rounds): | Place | Contestant | = | GR 13 | GR 14 | GR 15 | GR 16 | GR 17| | - | - | - | - | - | - | - | - | | ...

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Nebius Round 2 (Codeforces Round 1088, Div. 1 + Div. 2) # Hello Codeforces _After countless nights of yapping, bedfight duels, and failed zero cycles_ The authors of the [three](https://mirror.codeforces.com/contest/2124) [best](https://mirror.codeforces.com/contest/2190) [Div. 1](https://mirror.codeforces.com/contest/2201) of all time, [user:nifeshe,2026-03-18], [user:chromate00,2026-03-18], and I, have joined forces to create the Division $1+2$ round that will break the internet: [contest:2211], which will be held on [contest_time:2211]. This round will be combined for Division $1$ and Division $2$ and will be rated for everyone. You will have $2.5$ hours to solve $8$ problems. Between $6$ and $7$ problems will not be split into subtasks. Also, between $6$ and $7$ problems will not be interactive, so you are recommended to read the [guide](https://mirror.codeforces.com/blog/entry/45307) to interactive problems if you have not encountered them before. We would like to thank the following people for making the contest possible: - [user:Um_Nik,2026-03-2...

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Codeforces Global Rounds 2020: Current Results (GR7-GR10) In 2020 (as in 2019), with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds will be held. These will be common rounds for both divisions of 7–9 problems each. The duration of the rounds will be 2-3 hours, depending on the number and complexity of the problems. All such rounds will be rated for all participants. <i>At each such round, 50 brand T-shirts will be handed out, and we will be happy to give T-shirts to all problem authors and problem testers.</i> The prizes for the 6-round series in 2020: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. Current standings after four rounds (sorted by total points in four rounds): | Place | Contestant | = | GR 7 | GR 8 | GR 9 | GR 10| |--|--|--|--|--...

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Codeforces Round #614 Editorial All themes written by [user:Akikaze,2020-01-13] (I am the only one in the team playing Cytus II anyway :D). [problem:1293A] ------------------ Author: [user:xuanquang1999,2020-01-13] Development: [user:xuanquang1999,2020-01-13], [user:Akikaze,2020-01-13] Editorialist: [user:xuanquang1999,2020-01-13], [user:Akikaze,2020-01-13] <spoiler summary="Tutorial"> [tutorial:1293A] </spoiler> <spoiler summary="Solution (Akikaze, C++)"> Submission link: [submission:69149995] <spoiler summary="Source code in plain text"> ~~~~~ #pragma GCC optimize("Ofast") #include <bits/stdc++.h> using namespace std; #define endl '\n' int n, s, k; vector<int> a; void Input() { cin >> n >> s >> k; a.clear(); a.resize(k); for (auto &z: a) cin >> z; } void Solve() { for (int i=0; i<=k; i++) { if (s-i >= 1 && find(a.begin(), a.end(), s-i) == a.end()) {cout << i << endl; return;} if (s+i <= n && find(a.begin(), a.end(), s+i) == a.end()) {cout << i << endl;...

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Codeforces Global Rounds 2020: Current Results (GR7-GR9) In 2020 (as in 2019), with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds will be held. These will be common rounds for both divisions of 7–9 problems each. The duration of the rounds will be 2-3 hours, depending on the number and complexity of the problems. All such rounds will be rated for all participants. <i>At each such round, 50 brand T-shirts will be handed out, and we will be happy to give T-shirts to all problem authors and problem testers.</i> The prizes for the 6-round series in 2020: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. Current standings after three rounds (sorted by total points in three rounds): | Place | Contestant | = | GR 7 | GR 8 | GR 9| |--|--|--|--|--|--| ...

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Codeforces Global Rounds 2019: Current Results In 2019, with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds will be held. These will be common rounds for both divisions of 7–9 problems each. The duration of the rounds will be 2-3 hours, depending on the number and complexity of the problems. All such rounds will be rated for all participants. <i>At each such round, 50 brand T-shirts will be handed out, and we will be happy to give T-shirts to all authors and problem testers.</i> The prizes for the 6-round series in 2019: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. Current standings after two rounds: | Place | Contestant | = | Round 1 | Round 2| | - | - | - | - | - | | 1 | [user:tourist,2019-06-01] | 1706 | 1000 | 706 | | 2 | [us...

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New Year wishes from participants — "Cyan Rebellion 2022" survey results Hi! Two weeks ago I made a survey [link here:](https://mirror.codeforces.com/blog/entry/98424) about making Codeforces better. In this blog I am sharing the results. Consider reading the previous blog first, but this one should be self-contained as well. TLDR ------------------ The quality of Codeforces problems has increased over time, and people are mostly happy. Participants would probably be even happier with a greater variety of problem topics. It's important for setters to consider the contest as a whole, including the target audience of a given task. Some users wrote essays longer than the entire survey. How to access the results ------------------ Before we start, I would like to invite everyone to take a look at the raw data. If you are keen on showing off your data analysis skills, please do so! I hope that some of us will manage to find more interesting insights taking into account preferences of users from various skill groups. [Raw results](https://docs.google.com/...

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Russian AI Cup 2016 — CodeWizards Hey everyone! Good news &mdash; Russian AI Cup 2016 has started! This competition is being held for the fifth time, and this time, hopefully, we will make happy all the fans of the MOBA game genre &mdash; you will be controlling a wizard, and together with 4 teammates you will try to destroy enemy base with magic and help of minions. Try yourself in creating an artificial intelligence, it's simple and fun. Go to [Russian AI Cup site](http://russianaicup.ru) and enter the battle. Good luck! ### What is it? **Russian AI Cup** &mdash; largest annual artificial intelligence programming contest in Russia, and third open competition for talented IT-specialists that is part of Mail.Ru Group strategy of forming and developing competitive Russian IT-industry on a global scale. Following programming languages are supported: C++, C#, Java, Pascal, Python 2, Python 3 и Ruby. Anyway, as previously, we are ready to support language packages, realized by the community. We welcome bo...

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Codeforces Global Rounds 2019: Current Results After Five Rounds In 2019, with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds will be held. These will be common rounds for both divisions of 7–9 problems each. The duration of the rounds will be 2-3 hours, depending on the number and complexity of the problems. All such rounds will be rated for all participants. <i>At each such round, 50 brand T-shirts will be handed out, and we will be happy to give T-shirts to all authors and problem testers.</i> The prizes for the 6-round series in 2019: - In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT). - 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. Current standings after five rounds: | Place | Contestant | = | Round 1 | Round 2| Round 3 | Round 4 | Round 5 | | - | - | - | - | - | - | - | - | | 1 | [user:tourist,201...

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Eolymp Weekend Practice #8 ### **Hello Codeforces!** ------------------  I'm very super duper ultra excited to invite you to [Weekend Practice round #8](https://basecamp.eolymp.com/en/contests/8g2aerj14903raif9v7veir3m8) , taking place on [July 13, at 12:00 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=13&month=7&year=2025&hour=15&min=00&sec=0&p1=166). This is a **rated** contest at Eolymp. <h2>NOTICE THAT THE ROUND TIME SCHEDULE GOT EARLIER BY 1 HOUR</h2> #### **Format and Difficulty** Same as in previous rounds, the competition is primarily aimed at improving practical skills. There will be $2$ hours for $5$ tasks of varying difficulty, the easiest of which can even be solved by beginners. The scoring for each task being block-based (meaning points are awarded for each block of tests separately, and only if the solution passes all tests in the block). If there is a tie between...

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It is true that we are having fewer rated contests... _The story_: Five days since the last round and waiting for the next one makes me want to do something, and seeing posts a few days ago on "no upcoming contests", I somehow wanted to see if we really are having fewer contests. Below are the findings&#x2757; The data counts for all contests with a `div. [#]` included in their names and all global rounds. In specific, I counted their divisions, date, and participant number, and then visualized the data into two types of graphs: 1. Frequency count of rated contests by divisions, based on their month and year. 2. Average number of participants for a division in each month of year. #### Overall distribution <p align="center"> <img src="https://i.ibb.co/Dw7n8Ty/Screenshot-2024-10-04-at-17-13-44.png" alt="Image"> </p> There seems to be no clear trends of frequencies within a year (e.g., I was expecting there will be more during summer holidays), however, there is a faint decline in contests over the past two years &#x...

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Problems that I authored so far Hi everyone! Today I saw a discussion in AC Discord server about how many problems some people made for different competitions. It was sparkled by [this](https://mirror.codeforces.com/blog/entry/108595) CF entry. I haven't keep track of this before, so it made me curious to go through everything that I made and publish in a comprehensive list. I'm doing it mostly out of curiosity, but maybe it might be interesting for someone else too :) [cut]<br> | # | Date | Problem | Contest | Comment | |-|-|-|-| | 1 | Jan 2016 | [Sasha and Swaps](https://www.hackerrank.com/contests/infinitum14/challenges/sasha-and-swaps/problem) | Ad Infinitum 14 | Find a $T$-th root of a given permutation, while minimizing the number of swaps in which the root may be decomposed. | | 2 | Aug 2015 | [Sasha and swag strings](https://acm.timus.ru/problem.aspx?space=1&num=1799) | Ptz Summer 2015. MIPT Contest | Compute the total number of distinct substrings on all edges of a given string's suffix tree. | | 3 | ...

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Eolymp Blitz #1 ### Hello Codeforces ! I'm glad to invite you to the First [**Eolymp Blitz Round #1**](https://basecamp.eolymp.com/en/contests/k4s9lmqljd6ttcsrh0fm71hbec) on [**6th September, at 10:00 UTC**](https://www.timeanddate.com/worldclock/fixedtime.html?day=6&month=9&year=2025&hour=13&min=00&sec=0&p1=166) , a regular programming contest for beginners! This is rated competition for members with rating $\le 1600$. ## Format and Difficulty The competition is meant help you get started with competitive programming and improve your problem solving skills. You will be given **1.5 hours** to solve **5 problems** of easy difficulty. The scoring for each task being block-based, meaning points are awarded for each block of tests separately, and only if the solution passes all tests in the block. If there is a tie between two participants, the one whose last productive submission (i.e., a submission that added at least one point) was made *earlier* will be ranked higher in the leaderboard...

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Round #28 (Div. 2) + Special Prizes Hello, Codeforces! We are happy to announce that we're going to host a new contest at [csacademy.com](http://csacademy.com). [Round #28](https://csacademy.com/contest/round-28/) will take place on [Wednesday, May/10/2017 13:00 (UTC)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CS+Academy+Round+%2328&iso=20170510T13&p1=1440&ah=2). This round will be a Div. 2, meaning that the rating change will only affect users with a rating below **1650**. Unrated users will also be affected. High rated coders can participate unofficially. If you want to take part in this round you need to [register](https://csacademy.com/contest/round-28/) before the contest begins. As this is a Div. 2, it will consist of **5** tasks of more accessible difficulty. #### Special prizes This round will have 3 special prizes consisting of private coaching lessons with our contest coordinator, [user:wefgef,2017-05-08]. Each lesson will be conducted on Skype and will last for 1 hour and 30 minutes...

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CodeCraft-21 and Codeforces Round #711 (Div. 2) Editorial [problem:1498A] ================== #### [**Video Editorial**](https://www.youtube.com/watch?v=lV5cb8wh3sE) **Author and Problemsetting:** [user:ninja_28,2021-03-29] **Editorialist:** [user:sigma_g,2021-03-29] <spoiler summary="Hint"> Can you think of the simplest properties that relate a number and its sum of digits? </spoiler> <spoiler summary="Hint 2"> Note that if $X$ is a multiple of 3, then **both** $X$ as well as the sum of digits of $X$ are a multiple of 3! Can you put this property to use here? </spoiler> <spoiler summary="Hint 3"> If $X$ is a multiple of 3, then $\texttt{gcd-sum}(X) \ge 3$. Therefore, we are guaranteed that at least every third number will satisfy the constraints required by our problem $(\texttt{gcd-sum}(X) > 1)$. </spoiler> <spoiler summary="Solution"> Therefore, for the input $n$, we can simply check which one of $n$, $n+1$, and $n+2$ has its gcd-sum $> 1$, and print the lowest of them. </spoiler> <spoi...

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April Fools Day Contest 2021 — ZS Edition Hi everyone, April Fools is near and as usual we have an [April Fools Day Contest](https://mirror.codeforces.com/blog/entry/88840) on Codeforces this year. In addition to that, I usually try to host some form of mini April Fools Contest for my friends every year (or almost every year). This year, I am trying to host a bigger April Fools Day contest than usual and I invite everyone to participate! In view of the April Fools contest on Codeforces, the round will begin at [31 March 10pm (GMT+8)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=April+Fools+Day+Contest+2021+%28ZS%29&iso=20210331T22&p1=122) and lasts for exactly $24$ hours (and thus it will end ~35 minutes before the CF April Fools round). The contest will consist of several unusual tasks, and I hope that everyone will at least find something interesting. The problems will not be sorted by increasing order of difficulty (if the word difficulty is even applicable), so it is **highly advisable** to read (and try!)...

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Codeforces Round 1077 (Div. 1, Div. 2) Editorial We hope you enjoyed the problems! <spoiler summary="Rate the contest!"> <spoiler summary="Quality"> - Excellent contest - Good contest - Average contest - Bad contest - Horrible contest </spoiler> <spoiler summary="Difficulty"> - Trivial contest - Easy contest - Average contest - Hard contest - Impossible contest </spoiler> </spoiler> [problem:2188A] - Idea: [user:__baozii__,2026-01-29], [user:Tobo,2026-01-29] - Solution: [user:__baozii__,2026-01-29] - Editorial: [user:__baozii__,2026-01-29] <spoiler summary="Solution"> For $|p_{n-1}-p_n|$ to be divisible by $n-1$, either $p_{n-1}=1$ and $p_n=n$, or $p_{n-1}=n$ and $p_n=1$. Either way, we can construct $p$ backwards. For $i$ from $n-2$ to $1$, there will only by one possible choice for $p_i$, where $...

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Weekend Practice #7 ### **Hello Codeforces!** ------------------  I'm very super duper ultra excited to invite you to [Weekend Practice round #7](https://basecamp.eolymp.com/en/contests/uitnv9tt356kj7di2bqsabpps0) , taking place on [June 7, at 13:00 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=7&year=2025&hour=16&min=00&sec=0&p1=166). This is a **rated** contest at Eolymp. #### **Format and Difficulty** Same as in previous rounds, the competition is primarily aimed at improving practical skills. There will be $2$ hours for $5$ tasks of varying difficulty, the easiest of which can even be solved by beginners. The scoring for each task being block-based (meaning points are awarded for each block of tests separately, and only if the solution passes all tests in the block). If there is a tie between two participants, the one whose last productive submission (i.e., a sub...

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arvindr9 Stream 1 Hi Codeforces! I’ve decided to try streaming. Given that I was very active in competitive programming last year during Covid and have recently been inactive during the start of the new school year (and have gotten very rusty :p ), I have decided to revive my involvement in competitive programming by trying streaming. I will be streaming myself doing [Codeforces Global Round 16](https://mirror.codeforces.com/contest/1566) tomorrow [Sept 14 from 6:30 &mdash; 9 am EST](https://www.timeanddate.com/worldclock/fixedtime.html?day=14&month=9&year=2021&hour=13&min=30&sec=0&p1=166). In order to free up the rest of my day to do other work / destress, I will be streaming early in the morning in my timezone (EST). You will be able to find the stream at my Twitch profile https://www.twitch.tv/arvindr9

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[Codeforces Global Round 13] Pekora and Trampoline — O(n) Solution The basic idea here is the same as given in the [Editorial](https://mirror.codeforces.com/blog/entry/88248). So please read that first. Now to efficiently do this in O(n) we need to keep track of possible jumps Pekora can make from a given index. Suppose we have an initial array of {4, 2, 2, 2, 3, 2}. We will traverse from left to right. Now we will start from index 0 (with value 4) because it is greater than 1. We will take it as the starting point. One thing we can observe is that we need to use it 3 times until it becomes 1. In doing so we will make a jump to 4th, 3rd and 2nd index in the 1st, 2nd and 3rd pass respectively. So all we have to do is find a way to store this so that when we come to a new index we already know how many times we will come to this index. I used an array for this to store the range which will be affected by the current index. My Submission: [submission:108827845] ~~~~~ auto solve(vector<int> &A) { int i, j, diff, n = A.size(); ll ans = 0; ...

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Editorial Round 1 of Yandex.Algorithm 2018 <spoiler summary="Police Patrol"> First, let's try to find the largest block that two patrols can cover (hint, it's not k). For instance, we can have one patrol cover $1,2,\ldots,k$. and the other cover $2,3,\ldots,k+1$. So, we can split $n$ houses into blocks of length $k+1$. Now, we have to look at what to do with the leftover houses. If there are more than two empty blocks, we need two patrols to cover both blocks. If there is only one empty block, we only need one patrol. Thus, the answer can be computed by the formula in the code below <spoiler summary="code"> ~~~~~ n,k = map(int, raw_input().split()) print (n/(k+1))*2 + min(2, n%(k+1)) ~~~~~ </spoiler> </spoiler> <spoiler summary="Alphabetic Subsequence"> We can check that this is equivalent to counting the number of permutations of $0,1,2,\ldots,9$ that appear in $s$. There are two solutions: <spoiler summary="solution 1"> Just do it. This is O(10! * |s|) ~ 3*10^8. This is fast enough in some languages. ...

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A Recap of My First Year in CodeForces Hello all on Codeforces! ------------------ It’s been just over a full year since I created my Codeforces account. Since then a lot has happened on my Codeforces journey so far. With everything that’s happened I want to look back at how I got to my current point, share what I learned in the process, recap some of my best moments, and laugh at whatever I was thinking on a few of these contests, because a lot happened. The only issue is that there’s no way I’m going to detail all **60** contests I took part in 2022. Instead I’ve chosen to “award” the 9 most memorable contests, wheter it be because I did exceedingly well or self destructed in almost hilarious fashion. A few notes before I begin: No full solutions for any problems are shown in this post but there are code snippets and discussions that are spoilers for these problems. I apologize in advance. ### First Contest &mdash; [Hello 2022](https://mirror.codeforces.com/contest/1621) This was the first contest held in 2022, ...

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Almost same Today I have received my T-shirt of Global Round 13  （only change the number of the round） Btw，how does other round's T-shirts look like？I have only seen GR2，9，10，13 from me or my classmates. （Probably all the T-shirt for writers is same，I guess.

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Подготовься к респе::итоги первой недели Привет, Codeforces! Подошла к концу первая неделя челленджа. Время подвести её итоги. Неделя получилась очень насыщенной, поэтому думаю, что пост получится достаточно длинным. Суббота, 12/02: с утра написал отбор на городскую олимпиаду, ничего интересного. Вечером написал [contest:1637], написал очень плохо, не решил C, хотя это была очень простая задача. Очень понравилась D с этого контеста, нужно было сделать достаточно красивое преобразование формул, а потом решать рюкзаком. Оффтоп: начал замечать, что в последнее время много рюкзака стало. На ИОИП, на Global round, на Div. 2. Дорешивание: [<font style="color:#006400">C. Андрей и камни</font>](https://mirror.codeforces.com/contest/1637/problem/C), [<font style="color:#FFA500">D. Очередная задача на минимизацию</style>](https://mirror.codeforces.com/contest/1637/problem/D), [<font style="color:#8B0000">E. Лучшая пара</style>](https://mirror.codeforces.com/contest/1637/problem/E). Воскресенье, 13/02: Решал второй отборочный тур ИОИП. Напис...

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"Code Your Heart Out" @ CodeChef SnackDown-2016 Hello Everyone!, Finally the SnackDown 2016 has arrived and it has an overhauled [CodeChef’s](https://www.codechef.com/) kitchen with it. Its time to take due advantage of summer break and compete on a global level with the best programming brains from round the globe. Summon your teams and let the beast out of you for the 3rd edition of SnackDown programming championship. you can register your team having a maximum of 2 members from the same institution via link given below. Registration Link: [CodeChef/SnackDown/Registration](https://www.codechef.com/snackdown/2016/?REF=s_verma) **Contest Schedule:** 1) Online Registration : [06 May 2016 at 06:00 IST](http://www.timeanddate.com/worldclock/fixedtime.html?day=6&month=5&year=2016&hour=6&min=0&sec=0&p1=1617) -- [30 May 2016 at 21:00 IST](http://www.timeanddate.com/worldclock/fixedtime.html?day=30&month=5&year=2016&hour=21&min=0&sec=0&p1=1617) 2) Online Qualifier : [27 May 2016 at 21:00 IST](http://www.timeandda...

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Doubt in Solution for Codeforces Global Round 13 Problem B [problem:1491B] Let me just jump straight to my doubt: The editorial gives the solution as:  My concern is, why do we need to check for all the ai's? My approach was: 1. Since the whole first column will not be obstructed, the user can go directly to the last row. 2. Now, in the last row, there can be two scenarios: the obstacle is inline with the obstacle of the 2nd last row or out of line. a. If they are in line, then I have the option of moving either piece two units horizontally, or move the last obstacle diagonally upwards. Hence: ~~~~~ ans = min(2*v, u+v) ~~~~~ b. Otherwise, if the separation between the last and second last obstacle is equal to more than two, then the user can "slid in" between them without spending any coins. Hence answer in this case would be 0. c. Now if they are not in line and the condition **b** also fails, then I simply have to move the last obstacle either u...

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NowCoder Summer Multi-School Training Camp 2025 Hello, Codeforces! As the official team of NowCoder (China's leading programming competition platform), we are pleased to introduce the 2025 NowCoder Summer Multi-School Training Camp! This annual event has been running for eight years. Since the summer of 2018, we have collaborated with top competitors from algorithmic competitions such as ICPC, NOI, and IOI, aiming to enhance participants' programming skills through competitions, lectures, and exchanges, and to prepare for upcoming competitions like ICPC and CCPC in the second half of the year; simultaneously, we seek to foster learning and exchange among university training teams worldwide. <center> <h2 style="border-bottom: 1px solid #000;">Details</h2> </center> 1. **Schedule**. Consistent with last year, this year's training camp will consist of ten ICPC-style competitions, starting on [Tuesday, 15 July 2025<sup title="timezone offset" style="font-size:8px;" data-immersive-translate-walked="24cdac9c-eeae-41da-aef2-9dcf...

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Разбор Codeforces Round 990 (Div. 2 + Div. 1) ### Div2A Alyona is happy when there are no unfinished layers &mdash; that is, in front of her is a perfect square with odd side length. Since the order of pieces is fixed, it is enough to keep track of the total current size $s$ of the puzzle, and after each day check, if the $s$ is a perfect square of an odd number. The easiest way to do that is to create an additional array containing $1^2, 3^2, 5^3, ..., 99^2$, and check after each day, whether $s$ is in this array. <spoiler summary="Code"> ~~~~~ NT = int(input()) sqs = set() k = 1 while k * k <= 100 * 1000: sqs.add(k * k) k += 2 for T in range(NT): n = int(input()) a = list(map(int, input().split())) answer = 0 cursum = 0 for t in a: cursum += t if cursum in sqs: answer += 1 print(answer) ~~~~~ </spoiler> ### Div2B Find the character which appears the lowest number of times &mdash; if tied, take the earlier character in the alphabet. Find the character which appears the highe...

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A Confusing problem about F Magnets from Global Round 13 I came up with almost the same idea as the editorial . The only difference is that I queried $i$ and $i+1,i+2,...,n$ to find a magnet (I think it will be either the first or the second of them),instead of $i$ and $1,2,3,...,i-1$.And then I used the same approach just as the editorial says. However,I got TLE on test 6. qwq Today,I did a binary search on test 6.I get the test case that made me TLE, but it passed when I tested it locally. I do wonder why it goes wrong. You check my submission here [submission:108735158]

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PHSCO Fall 2025 Editorial Thanks to everyone who participated in the Fall 2025 PHSCO! Over 40 teams participated across both divisions, which is a new record and extremely inspiring for our second-ever hosted contest. Things went a lot more smoothly this year and we hope that all (or at least a majority) of the problems were enjoyable. On a personal note, being able to run PHSCO is an amazing opportunity and I can't thank all of you enough for making it possible. Anyways, without further ado, congratulations to all of the winners in each prize pool! Please check your emails for prizes, which should be sent out within this week. (If you don't receive anything after a week, please contact me!) **Standard Division (Pre-College):** - 1st &mdash; Entropy &mdash; [user:TheInfiniteLoop,2025-10-26] &mdash; Narayana Educational Institution - 2nd &mdash; 1 orz 1 norz &mdash; Eason Li, Ethan Chang ([user:easonli416,2025-10-26], [user:spoonspoon1006,2025-10-26]) &mdash; Ellen Fletcher Middle School, Davidson Acad...

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Main test for problem C2 is not strong enough (For codeforces global round 5.) There are some users who submit the same code for C1 and C2, but get main test failed for C1 and passed for C2. This JavaScript code shows that there are 12 users who passed C1 and failed C2: (run this in the developer console on a Codeforces page) <spoiler summary="Code"> ```js function sleep(ms){ return new Promise(function(resolve,reject){ setTimeout(resolve,ms) }) } async function custom_test(source,programTypeId,input){ // There's no official API // adapt from CF customtest js code const data=await $.post('/data/customtest',{ csrf_token: Codeforces.getCsrfToken(), source: source, sourceCode: source, tabSize: 4, programTypeId: programTypeId, input: input, output: '', // not _tta: 510, // ? communityCode: '', action: 'submitSourceCode', }) while(true){ sleep(2500) const response=await $.post("/data/customtest", { communityCode: "", action: "getVerdict", customTestSubmit...

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Lexicographically Minimal String Rotation -------------------- -------------------- -------------------- -------------------- -------------------- # <strong> <center style="color:red;"> Table of content </center> </strong> | Teleporter | Description | | :---------------------------------------------- | :----------------------------------------------------------- | | [I. The Problem](#problem) | Describe about the problem | | [II. Bruteforce Approach](#brute) | Simple way to do the problem | | [III. Hashing Approach](#hash) | Reduce circular substring comparing complexity | | [IV. Sqrt Decomposition](#sqrt) | Divide into parts, solve each part then solve the whole part | | [V. KMP Approach](#kmp) | Magical Linear Booth-KMP Algorithm ...

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Problem Topics Good Day to you! I've been asked to make some topic-wise list of problems I've solved. Even though I couldn't involve all problems, I've tried to involve at least "few" problems at each topic I thought up (I'm sorry if I forgot about something "easy"). I've alredy made such list once anyway I've tried to include more problems now &mdash; so here it is: <spoiler summary="aho"> http://www.spoj.com/problems/ADAJOBS/ URI 2226 (5) //[NICE][NUMBERS][DP] http://www.spoj.com/problems/SUB_PROB/en/ http://mirror.codeforces.com/contest/696/problem/D 8 http://www.spoj.com/problems/AHOCUR/ 5 //Aho-Corassic + DP https://www.codechef.com/problems/LYRC (5) //Sample aho-brute-force http://mirror.codeforces.com/problemset/problem/346/B //Proposed by [user:bradyawn,2019-08-03] </spoiler> <spoiler summary="automat"> 6861 [LA] //CYK UVA 10679 //Suffix Automat http://www.spoj.com/problems/STRMATCH/ //Suffix Automat &mdash; trie might do too http://www.spoj.com/problems/NSUBST...

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bug in rating change in global round 12 the second guy has a worse rank and more initial rating still he has more delta why

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Translation of the article by ko_osaga on Kinetic Segment Tree. I hear a lot about this topic but could not find any resources in Russian or English, so I decided to translate an article by [user:ko_osaga,2024-06-13]. This translation may contain many inaccuracies, and it lacks the links available in the original article. This article presents a new segment tree, called the Kinetic Segment Tree. An element is considered Kinetic if it moves over time, i.e., if the element represents a linear or polynomial function. Segment trees are often found in competitions, as are Kinetic elements (e.g., the convex hull trick), so studying their combination can also be useful. It is also worth noting that Kinetic properties can be identified even in problems not directly related to Kinetic elements (e.g., using CHT in DP optimization), and consider how the Kinetic Segment Tree can be applied. This data structure has already been mentioned in articles on Codeforces, but I recently found time for a more thorough study. At the time of writing, the Kinetic ...

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Invitation to Insomnia Qualifier 2022 Hello Codeforces! Computer Club, MNNIT Allahabad, India is glad to invite you to the annual programming competition of MNNIT, INSOMNIA, which is an ACM-ICPC style team programming contest of 2.5 hours duration held on Codeforces during its annual technical fest Avishkar. The team can consist up to 3 members. <b>Contest Details: </b> <ol> <li> Qualifiers: </li> <ul> <li> Start Time: Wednesday, November 9, 21:00 IST</li> <li> Duration: 2.5 hours</li> </ul> <li> Finals: </li> <ul> <li> Start Time: Sunday, November 13, 12:00 IST</li> <li> Duration: 2.5 hours</li> </ul> </ol> **Top 25** global teams, and **Top 25** teams from MNNIT (based on the result of Qualifiers) will qualify to the Finals. The prize distribution for global teams is mentioned below: <br>  Teams consisting of MNNIT students only will be eligible for a seperate prize pool. Register your team for the qualifiers here: https://forms.gle/BKsbKfoGzSxC394R8 <br>...

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mBIT 2025 Editorial Thank you to everyone who competed in mBIT 2025! It was a record breaking year for us with 84 in-person participants and 135 online participants. We hoped you guys enjoyed it as much as we did. We tried hard to make the problems fun and interesting for as wide of a skill gap as possible. In fact, this year's competition had an in-person team of middle schoolers that was unfamiliar with for loops, and an online team with all three participants in the top 15 in the world in codeforces. We are glad to contribute to all niches of the computer science community: beginner and advanced, local and global. Thank you all for your enthusiasm. Congratulations to the winners: **Online Advanced:** - 1st place &mdash; HoMaMaOvo &mdash; Masaki Nishimoto, Riku Kawasaki, Yui Hosaka - 2nd place &mdash; mathforcesbox &mdash; Brian Xue, Bing-Dong Liu, Alex Chen - 3rd place &mdash; bluepuppygreenturtle &mdash; Rain Jiang, Kai Jiang **Online Intermediate:** - 1st place &mdash; NULP Lega...

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National Competitive Programming Challenge — Editorial Here is the link to the contest: [Link](https://mirror.codeforces.com/contestInvitation/6071a436743e70518e953453aadcf924bca069aa) ### [A. The Blacksmith](https://mirror.codeforces.com/gym/656191/problem/A) <spoiler summary="Credits"> - **Problem Idea**: [user:eulmelk,2025-12-12] - **Problem Setter**: [user:eulmelk,2025-12-12] </spoiler> <spoiler summary="Rate the Problem"> - **How good is this problem?** - Very Good - Good - Bad - Very Bad - **How hard is this problem?** - Very Easy - Easy - Hard - Very Hard </spoiler> #### Approach 1 <spoiler summary="Tutorial"> **Step 1**<br> $n \le 500$, so the total number of pairs is at most $\frac{n(n-1)}{2} = \frac{500 \cdot 499}{2} = 124750$. This is easily manageable within time limits. **Step 2**<br> By checking every possible pair, we never miss any valid combination. Therefore, keeping the maximum among all va...

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