VK Cup 2017 Round 3 + Codeforces Round #412 (Div. 1 + Div. 2) Hi everyone! The last elimination round of VK Cup 2017, Round 3, will take place on May 7 at 18:35 MSK ([check your timezone here](https://www.timeanddate.com/worldclock/fixedtime.html?msg=VK+Cup+Round+3&iso=20170507T1835&p1=352&ah=3)), along with separate Codeforces Round #412 for both divisions. All three rounds will be three hours long, and all three rounds will be rated. The contest "VK Cup 2017 — Round 3" is for teams qualified from Round 2 or Wildcard Round 2. The top 20 teams will advance to the final which will be held in July 2017 in Saint Petersburg! Huge thanks to [user:KAN,2017-05-06], [user:qwerty787788,2017-05-06], [user:PavelKunyavskiy,2017-05-06], [user:AlexFetisov,2017-05-07], [user:MikeMirzayanov,2017-05-06], and VK company for making this round possible. Codeforces will be the main character of most problems. Don't forget that it's useful to read the statements of all the problems. Good luck! As we're in year 2017, the scoring will obviously be stat...

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VK Cup 2017 Round 3 + Codeforces Round #412 -- Tutorial Here is the tutorial of VK Cup 2017 Round 3 and Codeforces Round #412. Enjoy! <spoiler summary="Is it rated?"> [tutorial:807A] <spoiler summary="Code"> ~~~~~ n = int(input()) results = [] for i in range(n): results.append(list(map(int, input().split()))) for r in results: if r[0] != r[1]: print("rated") exit() for i in range(n): for j in range(i): if results[i][0] > results[j][0]: print("unrated") exit() print("maybe") ~~~~~ </spoiler> </spoiler> <spoiler summary="T-Shirt Hunt"> [tutorial:807B] <spoiler summary="More efficient code"> ~~~~~ #include <bits/stdc++.h> using namespace std; int main() { int p, x, y; cin >> p >> x >> y; for (int s = y; ; s++) { if (s % 50 != x % 50) { continue; } bool me = false; int i = s / 50 % 475; for (int j = 0; j < 25; j++) { i = (i * 96 + 42) % 475; if (i + 26 == p) { me = true; ...

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Codeforces Round 1044 (Div. 2) Editorial Thank you for participating in my round! I hope you all enjoyed it. <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:2133A] <spoiler summary="Hint 1"> What does the speed of each gear depend on? </spoiler> <spoiler summary="Solution"> Suppose we have some arrangement of gears where gear $i$ from the left has $b_i$ teeth. Then the speed of gear $n$ is $1 \cdot \frac{b_1}{b_2} \cdot \frac{b_2}{b_3} \cdot \ldots \cdot \frac{b_{n-1}}{b_n}$. Notice that most of the fractions cancel, leaving only $\frac{b_1}{b_n}$. So in fact, the speed of gear $n$ depends only on $b_n...

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The most upvoted rounds on Codeforces The top10 of them: | Rank | ID | Name | Upvotes | | :--: | :--: | :----------------------------------------------------------: | :----------------------------------------------------------: | | 1 | 913 | [Hello 2018](/contest/913) | [<span style="font-weight:bold;color:green">+2848</span>](/blog/entry/56954) | | 2 | 773 | [VK Cup 2017 &mdash; Round 3](/contest/773) | [<span style="font-weight:bold;color:green">+2247</span>](/blog/entry/51867) | | 2 | 806 | [Codeforces Round #412 (rated, Div. 1, based on VK Cup 2017 Round 3)](/contest/806) | [<span style="font-weight:bold;color:green">+2247</span>](/blog/entry/51867) | | 2 | 807 | [Codeforces Round #412 (rated, Div. 2, base on VK Cup 2017 Round 3)](/contest/807) | [<span style="font-weight:bold;color:green">+2247</span>](/blog/entry/51867) | | 3 | 10...

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A Slight Generalization of Push-Free Segment Trees Hi everyone! I'd like to share a simple way to use the [push-free segment tree](https://mirror.codeforces.com/blog/entry/112890) in some cases where the updates aren't commutative (spoiler: they need to be invertible). The uses cases of this trick are rather limited, though. The problem ------------------ We want to solve the following problem: Given an array $a_0, a_1, \dots, a_{N-1}$, whose elements satisfy certain properties (see [here](https://atcoder.github.io/ac-library/production/document_en/segtree.html)), answer $Q$ queries of the following types: - (Range queries): Given $0 \leq l < r \leq N$, find $a_l \cdot a_{l+1} \cdots a_{r-1}$ (endpoints are left inclusive and right exclusive). - (Range updates): Given $0 \leq l < r \leq N$ and a mapping $f$, update $a_i$ to $f(a_i)$ for all $i \in [l, r)$. $f$ has to satisfy the properties described [here](https://atcoder.github.io/ac-library/production/document_en/lazysegtree.html). Push-free segment trees ------------------ ...

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Me and DeepSeek spent a weekend analyzing 8000 CF problems. Here's what we found # Me and DeepSeek analyzed 1600 Codeforces contests and 8000+ problems — some interesting patterns please check this result : https://ayushgirigoswami.github.io/codeforces_analysis_report/ A few weeks ago I got curious about something most of us probably notice intuitively but rarely measure properly: * Is Codeforces getting harder over time? * Which topics are becoming more common? * Are some problems overrated or underrated? * How different are Educational rounds from regular rounds? So I wrote a Python script that pulls contest/problem data from the CF API, analyzes ratings + tags, and generates interactive visualizations. ### Report https://ayushgirigoswami.github.io/codeforces_analysis_report/ ### Source code https://github.com/Ayushgirigoswami --- ## Dataset The analysis includes: * 1600 contests * 8354 rated problems * Div.1 / Div.2 / Div.3 / Div.4 / Div.1+2 * 2011 → present Average problem rating across the dataset: **1793** --- ...

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Coder-Strike 2014: Раунд 1 Доброе время суток! Совсем [скоро](http://timeanddate.com/worldclock/fixedtime.html?day=18&month=4&year=2014&hour=20&min=0&sec=0&p1=166) начнется Coder-Strike 2014: Раунд 1. Напоминаю, что его официальными участниками будут школьники Москвы и Московской области, решившие на квалификационном раунде хотя бы одну задачу. Все остальные могут поучаствовать в раунде неофициально. Как обычно, для участия в раунде нужно зарегистрироваться на него на [странице](http://mirror.codeforces.com/contestRegistration/412). Раунд будет рейтинговым для всех официальных участников раунда, а также для неофициальных участников из второго дивизиона. Рейтинг по официальным и неофициальным участникам будет считаться отдельно. Раунд готовили я, [user:HolkinPV,2014-04-18] и [user:Igor_Kudryashov,2014-04-18]. Мы очень старались подготовить его как можно лучше. Если есть какие-то вопросы, не стесняйтесь, задавайте их в комментариях. Надеюсь задачи раунда вам понравятся. Удачи! **UPD 1.** Распределение ...

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Help: Geometry problem. Find colinear points. Prove this solution is wrong. DISCLAIMER: I really want to understand why this solution (which I think is quite reasonable) is wrong. If this is a nonsensical solution, please say so. I am not looking for a AC solution, I'd like to prove that this one is wrong, but i've been unable to do so.. ____ **Problem Statement** The statement is from [timus 1588 &mdash; Jamaica](http://acm.timus.ru/problem.aspx?space=1&num=1588): **Each two cities are to be connected by a road going along a straight line**. One road may connect several cities if they lie on the same straight line. Jamaican economists are sure that the new network will minimize transportation expenses. In order to estimate the cost of the project, it is required to **determine the total length of the roads to be constructed**, and this is the job for Andrey. ____ **Solution to be proven wrong** So, we have N points and we want the sum of a subset of the lines. Consider all point combinations, this give all lines. A line is described by...

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AtCoder Beginner Contest 412 Announcement We will hold AtCoder Beginner Contest 412. - Contest URL: https://atcoder.jp/contests/abc412 - Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20250628T2100&p1=248 - Duration: 100 minutes - Writer: [user:Nyaan,2025-06-27], [user:cn449,2025-06-27] - Tester: [user:toam,2025-06-27], [user:sounansya,2025-06-27] - Rated range: ~ 1999 - The point values: 100-200-300-425-500-525-650 We are looking forward to your participation!

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Региональный этап: результаты! ### **Привет, CodeForces!** Появились результаты регионального этапа по информатике. <spoiler summary="Баллы">  Мне очень обидно, я не призер( Самое ужасное, что у меня 412 баллов((( </spoiler>

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Error while trying to launch topcoder arena Please help me. I want to be able to participate in SRM 724. I got this error when trying to launch topcoder arena. ~~~~~ Exception in thread "main" java.lang.UnsupportedClassVersionError: net/sourceforge/jnlp/runtime/Boot : Unsupported major.minor version 52.0 at java.lang.ClassLoader.findBootstrapClass(Native Method) at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1073) at java.lang.ClassLoader.loadClass(ClassLoader.java:414) at java.lang.ClassLoader.loadClass(ClassLoader.java:412) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:312) at java.lang.ClassLoader.loadClass(ClassLoader.java:358) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482) ~~~~~ I'm running it on Achlinux using icedtea-web

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(ReView) Gấu em là hot girl................................................................... - conglb Các thím cứ xem đây là một câu truyện nhé , vì không muốn ảnh hưởng tới cuộc sống của em và gấu nên một số info em đã thay đổi, hi vọng các thím đừng lùng info của em ! Chúc các thím có những giây phút hạnh phúc bên gia đình và người thân ! Chap 1 : Chào các thím trong Voz , em biết tới voz khá lâu, toàn vào đọc truyện của các thím thôi nên hôm nay quyết định viết đôi dòng tâm sự mà cũng có thể nói là một câu truyện về cuộc đời e ( tin hay không tùy các thím, cứ coi nó là câu truyện để đọc , để cảm nhận và để biết cuộc sống muôn màu nhé ) . Hi vọng các thím hết lòng ủng hộ em, văn em dốt nên có chỗ nào không ổn các thím thông cảm nhé. Với trong lòng đang vui vì hồi chiều chen lấn cũng mua được cặp vé xem U19 Việt Nam đá, may chiều nay mua chứ mai chắc là hết cmnr. Chỉ đợi gấu đi công tác về, cuối tuần sau 2 đứa đi xem đá bóng, đây là lần đâu tiên em xem trực tiếp tại Mỹ Đình, không biết có vui hông ? À giới thiệu qua với các thím , em là sinh viên năm cuối ở một trường ĐH ở...

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Who participated most? **UPD:** The calculation updated, for some reason I filtered only CF style competitions. Now it includes everything. Still [user:ruban,2024-08-07] best :) I revisited some data from Codeforces and, [after 5 years](https://mirror.codeforces.com/blog/entry/72410), decided to calculate again who has participated in the most contests. I took into account all official contest participations, including those where a user participated unofficially. However, I excluded Practice/Virtual contests. P.S: I think no one will beat [user:ruban,2024-08-07] ever :) |Rank|Handle|Total|Official|Unofficial| |---|---|---|---|---| | 1 |  [user:ruban,2024-08-13] | 1164 | 1090 | 74 | | 2 |  [user:kmjp,2024-08-13] | 972 | 547 | 425 | | 3 |  [user:dreamoon_love_AA,2024-08-13] | 891 | 538 | 353 | | 4 | ![ ](https://mirror.codeforces.com/codeforces.org/s...

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Activity Calendar Not Updating After Accepted Submission Hello Codeforces team, I’d like to report an issue with my activity calendar. Yesterday, I solved a problem for the first time, which I had never solved before, and received an AC (Accepted) verdict. However, the calendar still shows a white dot for that day. Problem: Codeforces Round #412 (Div. 2), Problem B &mdash; 3-palindrome My Submission: https://mirror.codeforces.com/contest/805/submission/320796105 Since this was a new problem for me and it was solved yesterday for the first time, I expected the calendar to reflect that with a colored dot. This looks like either a bug or a delay in calendar updates. Could someone from the team please take a look? I’d appreciate any help resolving the issue. Thank you for maintaining such an amazing platform! Best regards, _Break_The_Limits_

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Hack me! — Year 2014 in review! (part 1.) Hey there! Since new year is coming, I want to start little summing-up of the ending one (of course we still talk about hacks :)). I wrote another short script, which purpose was to summarize all hacks in the 2014. I wanted to upload it after two last rounds, but mostly because of little differences (especially between first and second place), I did it before last rounds. Maybe the next rounds will be more exciting because of it. Below there is a list of 50 best hackers in this year <s>(so far)</s>, the full list can be found [here](http://test.weaselcrow.com/pro/cf/hack2014/). <strong>Update: </strong> After last round, the ranking was updated. The last round was decisive: [user:mosiomohsen,2014-12-31] made 5 successful hacks and 1 unsuccessful and with 450 points, he managed to surpass [user:anta,2014-12-31]. Congratulations! [cut] <div></div> rank | handle | points | best rounds | accuracy | :---:|:---:|:---:|:---:| 1 | [user:mosiomohsen,2014-12-31] | 8...

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Региональный этап: день 2 #### **Привет, CodeForces!** Без долгих вступлений, я набрал $100+100+10+15=225$ баллов. Даже лучше, чем в первый день + я решил B, чем был сильно удивлен (так не всегда получается). В сумме $100+41+46+100+100+10+15=412$, для меня не плохо!

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Hack me! — Year 2014 in review! (part 2.) Merry Christmas everyone! One round behind us, one more to go in this year. It's time for the second part of my little summing-up (last post can be found [here](/blog/entry/15326)). Now we will show all most accurate hackers. We will count the accuracy as the: $$\frac{\#successfulhacks}{\#allhacks}$$ Because there were a lot of flawless hackers, below we show only hackers with at least 10 successful hacks &mdash; still there were 36 of them! The full list of hackers' accuracy can be found [here](http://test.weaselcrow.com/pro/cf/ahack2014/). Also, below this table there is updated list of best hackers by summarized points, also the full list was updated [here](http://test.weaselcrow.com/pro/cf/hack2014/). [cut] <div></div> ### Accuracy rank | handle | accuracy | best rounds | points | :---:|:---:|:---:|:---:| 1 | [user:hetanglianyi,2014-12-25] | 100.0% | <small>[contest:462] [+19-0]</small> | 1900 (+19-0) | 2 | [user:bmerry,2014-12-25] | 100.0% | <small>[c...

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Республиканская олимпиада 2022 год. Казахстан 2021 : https://mirror.codeforces.com/blog/entry/90111 2020 : https://mirror.codeforces.com/blog/entry/80808 2019 : https://scoreboard.bc-pf.org/results/informatics/national-olympiad/2019 2018 : https://mirror.codeforces.com/blog/entry/58432 2017 : https://mirror.codeforces.com/blog/entry/51416 #### 9 класс <table> <thead> <tr> <th>Место</th> <th>ФИО</th> <th>CF handle</th> <th>Балл</th> <th>Медаль</th> </tr> </thead> <tr> <td>1 </td><td>Таймас Мансур</td><td>[user:gamicrab,2022-04-19]</td><td>322</td></td><td><img alt=" " src="/predownloaded/93/73/9373156f429b185ba6bc779f81d16894f9a72d9e.png" style="max-width: 100.0%;max-height: 100.0%;"> </td> </tr> <tr> <td>2 </td><td>Абжами Ерсултан</td><td>[user:syrtin,2022-04-19]</td><td>274</td></td><td><img alt=" " src="/predownloaded/93/73/9373156f429b185ba6bc779f81d16894f9a72d9e.png" style="max-width: 100.0%;max-height: 100.0%;"> </td> </tr> <tr> <td>3 </td><td>Шермаханов Ильяс</td><td>[user:Tenjin,2...

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Couldn't Understand The Logic https://mirror.codeforces.com/problemset/problem/412/B I couldn't understand the logic behind the first tutorial (**not** the bruteforce one). Can anyone help me?

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Milestones: ratings above 1500 and greatest falls (2024 edition) <i>Note.</i> This is an updated version of [this post](https://mirror.codeforces.com/blog/entry/104681). If you like [this style](https://mirror.codeforces.com/blog/entry/104320) more, please tell me in the comments. Since [user:tourist,2024-09-05]'s [breakthrough](https://mirror.codeforces.com/blog/entry/133401), I've received a lot of requests to update my old posts with rating achievements. However, I wasn't able to do it immediately since my method of doing it requires to download the rating change history of every user, which, in turn, requires to perform several hundred thousand requests to Codeforces, about which the website (and Cloudflare) is not happy. It took more that three days, but finally the job is done! Below are two tables. The first one is the greatest (by absolute value) negative rating changes. The second one is the first users ever to reach some rating value. [cut] First table: <spoiler> <table> <tr> <th>Place</th> <th>&Delta;</th> <th>Person</th> </tr> ...

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Teams going to Gwalior/Pune Regionals **UPDATE:** I've uploaded the code that I used to generate this on Github, in case someone needs to generate something similar: [Codeforces Team Rating Calculator](https://github.com/abdullah768/Codeforces-Team-Rating-Calculator) The regional round has ended and here's the final Ranklist: https://www.codechef.com/public/rankings/ACM18GWR Inspired by the list of teams going to Kharagpur regionals, I decided to make one for Gwalior/Pune regionals. The list contains all the teams from the official Gwalior website. If you know the usernames of members of any of the teams. Please update the excel file: ### [HERE] (https://docs.google.com/spreadsheets/d/1jRvwzQzp1DOcazgI7jXBB8uY3u7Ze_eQ77Xa75_Q810/edit?usp=sharing) Team rating calculation has been done according to the official Codeforces team rating calculation formula. The table will be updated with details from the excel file every 6 hours or so. Last Updated: 10 pm, 12th December IST | No. | AIR | Team Name ...

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