Wind_Eagle's blog

By Wind_Eagle, history, 7 weeks ago, translation, In English

Hello, Codeforces! I, like many of you, read blogs periodically. Lately, blogs from low-rated users who ask me how to raise their ratings have been catching my attention. I want to tell you a little bit about my opinion on these blogs.

So what do these blogs look like? Usually this is a blog with a title something like "I need help right now!" or "How to improve my rating, help me!" When you open this blog, you see the most detailed description of the problem, such as: "I have solved 500 problems, but no improvement" or "I have solved 100 problems with rating >= 1500, but my rating is not increasing". And in the comments they usually write "you haven't solved enough, solve more" or "solve more difficult problems". In my opinion, this is incorrect and misleads such users.

So, imagine that you do not know anything at all about sports programming, or even about the basics of Olympic math. You at best (because many people don't even do that) have learned a programming language at a basic level (really, who needs templates and classes), such as C++. And so, you decide to become a sports programmer to get a job interview enjoy solving interesting problems. Imagine yourself as this person. Can you? No, imagine please, it's important.

When you have imagined this, imagine now that you have no friends at all who know what programming is. "Programming, huh? Is that edible?" Well, I'm kidding, of course, but it could very well be that no one around you is into programming. So, now there is a question. How to improve?" "What's a stupid question?" — you ask, "of course, just go and solve problems!" Just everything, and maybe some ladder (which I don't know much about). So, I declare: in my opinion, this is very bad advice, which will only harm someone who starts his way in sports programming. You have imagined yourself as a beginner, haven't you? Now think about it: if you only know high school math, can you solve D2A? If you think you can, I'll let you in on a secret: if you are not a born genius in sports programming, you probably can't.

Let me tell you a little about why. As can be seen from my profile, I'm from Belarus, from the city of Mogilev. In this glorious city there is a glorious gymnasium number two, where my wonderful EIK teacher teaches. She has many Olympiadists, both beginners and very experienced, like Dmi34, and a bunch of experienced, among them, for example, me, as well as another international master and international grandmaster. And I can tell you: if you take the beginners now, I'm not sure that they could solve even D2A in the first year at once. I'll explain why.

The whole point is that even D2A should actually be approached gradually (unless, of course, you have experience in math olympiads, say — then solving D2A in general is not a bad idea). Back to our mental experiment — take any random D2A from the last two years.

Totally randomly I chose round 672 and Problem A from it (1420A - Cubes Sorting). Think about it: How easy is it for someone who only knows school math to solve this problem? For example, in our university department we have a small section (for one or two lectures) devoted to permutations, and from this knowledge it is easy to solve this problem. But if you only know school math (and you have an ordinary, unremarkable school), then solving such a problem will obviously not be that easy. Actually, understanding that an unsorted array can be sorted by a bubble sort in n * (n-1) / 2 operations is not that hard, if you reason logically. As I see it, it is harder to show that for an unsorted array this does not hold.

Or round 697, problem A (1475A - Odd Divisor). Of course, this problem can be solved by simply writing out all the numbers on a piece of paper and finding a pattern. But here you need to know what is decomposition of a number into prime factors, know that it is singular, and so on. Thinking back to the greedy algorithms, I can mention the problem from round 765, problem A (again chosen at random) (1625A - Ancient Civilization).

My point is this. You need to know mathematics for sports programming. Now imagine: someone has solved, say, 100 problems A. Consider that most of them do not contain any new and interesting ideas at all, but just, as they say, ad-hoc. So what will one learn from these problems? I'm not sure, but it seems to me that simply nothing! One will remember twenty ideas, but the twenty-first will still be different. Going back to our imaginary newcomer: he has no one to ask, no one to ask to explain. No one to explain the standard ideas and approaches. So what does he have to do but cheat to write blogs?

The situation with problems B, C, and D is even worse. To solve them, you usually need to already know the standard ideas. The problem is that in order to practice these standard ideas, you need to solve problems on these standard ideas, not immediately D2C — D2D. Imagine if you were learning a segment tree right away from a 3000 difficulty problem. That's not very good.

To conclude the first part of the blog: Codeforces — is definitely not a place for beginners to practice. While more experienced users can practice here, it is hardly suitable for beginners. What to do, I do not know, and why I do not know, I will explain later.

Now let's move on to the second part. Now I want to explain why I think the Codeforces complexity approach is a bad idea.

Let's take a look at a few (again, totally randomly chosen tasks). Let me tell you right away: this will be my subjective opinion. Let's look at problems 858B (858B - Which floor?) and 996B (996B - World Cup). I consider the first one very simple for its complexity, and the second one — very difficult. I solved both problems long ago, but I only remember that when I was a pro, I solved the first one, although with difficulty, but when I was a candidate master, the second one was very difficult for me — I don't even remember if I solved it or not!

This is not to say that the tagging system on Codeforces is not very good, and often confusing. For example, in the DP topic you may come across a prefix-sum problem, and in many tasks the tags are put on the principle "here is a problem on ST/DP/bit operations. But it can be solved with flows. Let's put the tags: graphs, flows. Oh! You can also use ternary search! So let's do it!" So tags really don't always reflect the topic of the problem.

My point is this. You have to train by theme (but tags are also broken), not by difficulty. Especially when you're not that experienced yet. Don't be afraid that you can't do ad-hoc tasks — the main thing is to be good with standard ideas.

Many commenters who write "solve more problems" have, in my opinion, simply (and that's okay) forgotten what it's like to be gray or green. And that's okay: I don't remember solving while I was down, either. But looking at the way my instructor has been giving exclusively standard problems and approaches for a year or two, I'm starting to realize that she's probably doing it right.

Going back to our example — how would such a person know which topics are standard and which are not? At most he can only know the names of the topics. And by the way, apparently, this explains so many gray people who learn the Cartesian tree and Mo algorithm — they don't quite understand what things are needed at what level. And why don't they understand? In my opinion simply because there is no one to explain. So if you're a newbie/pupil and you're reading this, know — you need to learn approaches, not algorithms. And algorithms are better not to learn, but to understand. You should probably learn an algorithm when you encounter a problem at least once/twice in which you can bring the solution to completion, completely and independently, if someone had written the algorithm for you. That is, you have thought up all the steps, all the math, reduced the problem to a well-known algorithm — then you can open it and try to understand it. By the way, if you can't understand it, you can learn it for now — it seems okay to me. You can go back later for understanding (when you have more experience). When I was an expert, I didn't understand the segment tree (really, I was a high school student then, and not even a senior).

So, smoothly passing to the main idea of this blog — I can't imagine how you can practice without a coach. Of course, when all the basic ideas are studied, and the algorithms are perfected, you can move without a coach. But, say, to an expert or even to a candidate master will be much harder without a coach. I know that there are a lot of people who have studied on their own, and reached the heights. It seems to me that you — this is more of an exception to the rule than the rule. I'm very glad that you're doing well. But personally, I realize that without a coach, my progress would have been much slower.

I know that if people who came here to train for interviews. Guys, this is not the place for that at all. That's what LeetCode was invented for — there's a bunch of great problems to prepare for, I've solved a dozen or two myself.

Lastly: in my opinion, Codeforces should decide: should it still be a training ground for beginners, or should it only be a training ground for more senior ranks? Because if it's supposed to be a training ground for greys/greens as well, it doesn't seem to be. Because Educational rounds aren't Educational at all, they're regular Div. 2 rounds, which are only slightly more standard in terms of ideas and approaches. Even Div. 3 rounds, which are designed for greys and greens, have recently started to contain ad-hoc rather than standard tasks again. I understand that this is done for ranking consistency. But let there really be simple tasks for newcomers. In the Edu section there are problems on standard algorithms — believe me, learning these algorithms won't do much good for gray or green.

Therefore, if one wants to create a more favorable environment for beginners, make separate, perhaps unrated, practice rounds. I understand that a lot of effort is put into each Codeforces round by the authors, coordinators, and organizers (myself the author of two rounds and co-author of another one). Maybe that's why Codeforces will probably remain what it is. And you know what? I'm only going to be glad. Surely (but I don't know for sure), there are plenty of places for newbies to train. Let Codeforces remain as great as it is now, with ad-hoc challenges. In my opinion, that's what makes the rounds so interesting and exciting (just please don't make all the tasks on one topic. I won't give you examples, but there are some. Believe me, it's not cool).

Thank you Codeforces for being there!

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By Wind_Eagle, 4 months ago, translation, In English

Hello, Codeforces! Codeforces #765 (Div. 2) took place not so long ago, and one of its authors was me. When an hour had passed since the contest started, I decided to remember the old days and start making fun of the cheaters.

To that end, I decided to take a look at the old cheater groups and see how they were doing.

The first group I looked into — is the group where the admin is actively fighting against cheaters. So, there really weren't any cheaters on the round. I think that's a success.

The second group I checked out — it's a group with 2.5k users. I decided that just going in there would be too boring, so I decided to write there that I was a contest author. Here's the reaction of the users:

Picture

Can you imagine?! I write that I am the author of the contest, and I am offered to leak the solution to problem C.

As in the last blog, I wrote a completely wrong solution to Problem C so that cheaters would send it and get WA, and then they would get banned by the anti-plagiarism system.

That's the solution:

Code

I just dropped this code into the general group:

Picture

There are two interesting things here. First — some cheater wrote that "this code takes TL because it has two nested loops". Apparently cheaters don't know how to measure a time limit of a solution, and just think that two nested loops is bad. They probably just learned that it doesn't work in many problems, so they don't even think about writing it. By the way, that problem was $$$n \le 500$$$.

The second — I was banned from this group. Whatever.

But before that, a man wrote to me... You can read our correspondence yourself.

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Then I decided to find a new group. And I found a group with... 7.5k people! I was so surprised! I decided to write there that I had the solution to Problem C.

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I've had a lot more cheaters writing to me than I ever expected! By my calculations, I had about 20 people write to me, though usually not more than ten.

At first, I was just sending out solutions via private messages. From time to time people would asked me how much it costs, but I told them that I was giving them away for free.

But then a man wrote to me and asked me what my nickname on CF. I told him honestly that I am Wind_Eagle. And he asked me... what's the best way to train. I told him honestly. You can read what I advised him.

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But I stopped communicating when I realized what he was really into sports programming for.

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Then an apologetic cheater texted me... He apologized for cheating and promised not to do it again.

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Then, of course, they started writing about how my solution was wrong. I, of course, replied that it was their problem.

Picture
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Now I show you the funniest screenshots that I was able to make:

Tip for the cheater about the wrong solution idea so he at least learns some algorithms:
A cheater who is sure that the DP problem is solved by the stack, and does not want to make a solution without the stack, and does not know how to estimate running time:
I don't have a right solution, only a left solution:
Russian memes, as well as an admission that I am the author of the contest:
Cheater doesn't realize he's a cheater:
Rickroll:

And the conclusion, as usual, is the same: cheating — this is a much bigger problem than it seems.

P.S. By the way, we got a couple of personal messages on Codeforces during the round:

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P.P.S. Cheaters, be afraid — maybe I'll come to your groups again!

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By Wind_Eagle, history, 6 months ago, translation, In English

Hello, Codeforces! Today there was the second stage of the Republican Olympiad in Informatics in Mogilev region (Belarus). And I, as the author of this contest, decided to share this contest with you.

I have posted this contest in the gym by the link: https://codeforces.com/gym/103464

Contest rules: contest has 4 tasks for 5 hours, and it has IOI format, i.e., scores and subgroups. As for the difficulty of the contest, I think it will be interesting for people with a rating of 2000 and below, because the most difficult problem in it is not above the level of D2D — D2E.

There is no editorial yet.

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By Wind_Eagle, history, 8 months ago, translation, In English

Hello, Codeforces! A month ago I have wrote my blog about cheaters. Under that blog, a number of suggestions have accumulated, and there is a number of interesting ideas that could be applied to sabotage a group of cheaters.

I've often seen comments along the lines of:

Pictures

Well, doing what Sexpert suggested wasn't really what I wanted to do, but it was worth checking out what would happen if the wrong solutions were sent. I asked some famous user what would happen if I sent the wrong solutions to cheaters. He told me that someone had done this before and that he was quickly debunked.

I wondered whether I could cheat cheaters without getting caught. But for this, I had to do something. As you may remember from the last blog, I had already been featured in various cheater groups. So I needed an assistant to correspond with cheaters instead of me. That helper turned out to be Dmi34. Thanks a lot to him, without him this blog wouldn't have come out! We were on Discord and I told him what to do. He also helped me with writing code, but more on that later. By the way, don't scold him for his knowledge of English. His first language is Russian, after all.

My first idea was to create a group on CF and invite all cheaters there. Then I decided, that it's not a good idea. That's because it's almost impossible to get cheaters into a group on CF because they would probably realize that it would be a bad idea to leak their nickname. Yes, and how to lure them there? They obviously don't need trainings and training tasks.

So, I decided to stop at dropping the wrong solutions. Since I had been told that it could not be done, I wondered: why could it not be done? As it seemed to me, I found the answer. It was that the cheaters can't be sure that they have the right solution. So we did the following.

Dmi34 started to solve the problems in the round (don't worry, he's not a ranked participant since he's a candidate master), he solved problems A, B, D and E1. After that, we decided to do wrong solutions to problems D and E2. But we had to do it very carefully, because it was impossible to give them even the slightest hint about the solution. Then we did the following: I wrote the wrong solution for D, which takes both WA and TL (although cheaters often don't understand the difference between the $$$O(n \cdot log(n))$$$ and $$$O(n^2)$$$ solutions). And Dmi34 wrote a brute-force solution on E2, which obviously didn't work.

Links to these codes, they will help you catch cheaters:

So, Dmi34 wrote in the chat:

Pictures

And a wave of cheaters went down! Everyone wanted to know the solutions! We made them wait for a while, and then we started sending them these solutions after all. Here are the funniest and most interesting screenshots of their requests.

Pictures

We even had two people write to us asking for help with their admissions tests! I'll show you screenshots of one of them.

Pictures

They soon started to suspect something, but we dispelled their doubts with a screenshot: the rectangle is green, my solution works, look for a bug yourself.

Pictures

By the way, the cheaters took quite a while to respond. Apparently this is because they were changing the codes to avoid getting caught by anti-plagiarism. However, we still forced them to throw our code unchanged:

Picture

Soon some cheater wrote that he had a solution to the C problem. We messaged him that we want it, but he didn't reply to us. Soon we still find out how much the solution to the problem costs.

Also, some cheater wrote to us, asking us to exchange the solution to problem C for problem E2. To my deepest shame (sarcasm), we agreed, and dropped him the wrong code, and got his code in return.

Pictures

Here's his solution. By the way, it doesn't seem to work:

Cheater's Solution

After having a lot of fun, we decided to admit that they were just being trolled, and threw them funny messages. I thought they would react to it, but almost everyone was cool with it. Amazing calm!

Picture

What's funny, Dmi34 kept getting messages asking him for the solutions! Didn't it get to them even after reporting that they were being trolled? It feels like they just don't read the conversation!

The funniest cheater we have found:

Picture

Next, I personally joined another group with cheaters. I don't want to advertise them, but their admin wrote a comment under my last blog, you can check it out if you're interested. To my surprise, they... Really banned from texting during the contest! As soon as I joined, the bot wrote a message saying that Wind_Eagle had joined the chat... And I immediately (!) got a message from some cheater who offered me to buy the solution to his problem C. I asked how much the solution cost. So, now, without looking in the spoiler, try to guess how much it costs, and then stop by and check yourself.

Answer

I haggled for decency. When he said he was ready to sell, I wanted to write that I didn't need it, because I supposedly just thought up the solution to the problem. But he texted me his wallet number. I will not show it, I do not remember it and his number deleted, because it is too much. However, the cheater himself, I put him on blacklist so he wouldn't write to me again.

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Speaking of cost. Remember that group that asked for help with the test? Well, helping on a hiring test costs a mystical <<200>> (I suspect rupees).

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Now it's worth telling about my correspondence with the admin of this group. Why tell me about it though, read it for yourself.

Pictures

So, what can be learned from this blog? First of all, cheater catching enthusiasts — your turn! You can see the codes I sent them, and if you want, you can look for cheaters. Second, I showed you how much the solution costs and how actively they sell. And third, I showed that the tests for joining the company are also being bought and sold, which was particularly disappointing to me.

So what conclusion can be drawn from all of this? This. Cheating — it's not just cheating, it's also a business! So, like any semi-legal business, it is extremely difficult to eradicate.

P.S. Dear cheaters, please forgive me for the inconvenience! I did not want to hurt you too much, in the end, you will get back your rating in a couple of contests. All our wrong solutions you got as quickly as possible and for free . If I caused you any inconvenience, please forgive me! I won't do it again!

P.P.S. Thanks gepardo for checking the blog.

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By Wind_Eagle, 9 months ago, translation, In English

Hello, Codeforces! Not too long ago there was my second round, Codeforces #741 (Div. 2). Before it started, I wondered: surely there will be a lot of cheating on my round, just like on any other? So I decided to do something unusual.

As you know from a blog about cheaters, it's easy to find telegram/youtube channels with cheaters. So I decided to find a couple and join them...

So, the first telegram group I found was [link not available yet]. There weren't too many cheaters in it but they were, here's an example:

Picture

I joined this telegram group, and there was a meaningful dialogue:

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This may seem unbelievable, but the admin of the group actually banned participants from texting for the duration of the contest! So, I've already had at least some impact on the level of cheating during my contest. By the way, this channel published a couple of videos on my 1562A, 1562B and 1562C editorials. Pretty good ones, by the way.

The second group I found was probably the largest group with cheaters on telegram: [no link yet]. I repeated the procedure:

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However, this group ignored my appearance! And continued, as if nothing had happened, exchanging solutions in private messages or somewhere in discord:

Picture

A little later, they even wrote half the solution for problem 1562A:

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Some famous user came to my rescue:

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As you can see, the practice of swapping solutions is extremely popular in the cheat community (give me a B and I'll give you a C):

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However, there are cheaters who are also scammers! Apparently, he got the solution of another cheater and he didn't sent his solution to this cheater:

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And then something extremely interesting happened. I started getting personal messages from... Cheaters themselves! And they started to expose other cheaters! Apparently, they have absolutely no cohesive team.

One man (I am very grateful to him), gave me links to a couple of youtube channels, where there were cheaters. On one of them I went in the middle of the contest and also wrote in the comments, but I'll talk about that later. By the way, on one of the channels we can see the nickname of the author. A little later, when it comes to youtube channels, I'll show you who it was, and hopefully he will get banned.

So, here's what was written to me about youtube channels:

Picture

Somebody couldn't even believe that I actually authored the contest:

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Unfortunately, I don't have the most interesting messages saved because I blocked this cheater for direct insults, but to summarize, there were messages like this:

  • Hello, are you really Wind_Eagle?
  • Yes, this is me))
  • Nice contest, bro, but too hard for newbies.

After 30 minutes

  • Your contest is good, but task B is weird trah, sorry.
  • Why?
  • Because it is hard. Set your next contest without such bad tasks.

After 30 minutes

  • You are not Wind_Eagle!
  • Why do you think so?
  • Because contest author will be busy during the contest!
  • I am busy, but can take a break when I don't have many questions.
  • No, you are not Wind_Eagle, I knew it!
  • Why?
  • Because you are a [censored] idiot!

And then I banned him in Telegram.

The third and final group was a relatively small group of cheaters [no link yet]. By the way, this group was suggested to me in the personal messages by one of the cheaters from the previous two groups. I repeated the procedure here. There was an unexpected meeting with a fake of a known user and also I wasn't believed that I am Wind_Eagle:

Picture

In fact, I found it interesting to watch people refuse to believe that I am really the author of the contest. They threw funny smiley faces and jokes, but they couldn't admit it. Even when I made a screenshot showing that I was in my account and could edit the announcement, they still wouldn't believe me, saying that I had edited the HTML page. So, dear cheaters! I'm real! :)

Now let's talk about youtube channels. I found two of them: [link not yet] and [link not yet]. Unfortunately, the second channel has already finished broadcasting, so I left him a funny comment:

Picture

By the way, here's a screenshot of his screen:

Picture

I hope he will get banned.

I don't have any screenshots from the first channel, unfortunately. All I can say is that I wrote a message there, "Hi, I'm Wind_Eagle. Stop the stream or you'll be banned." By the way, in the comments, unlike in telegram, the tasks were discussed much more openly, codes and ideas were exchanged there in public.

Now a little bit about the good stuff. I received quite a few messages from users of these cheat telegram groups, in which they... say thanks for the contest! I've chosen a few of the best ones:

Pictures

What does one want to say as a conclusion? It's all very sad, frankly. There are not just a lot of cheaters. Not just very many. There are too many of them. I'm afraid that there is only one way to fight cheating on CF: to close such telegram/youtube channels. Otherwise there is simply no way to deal with this problem.

In conclusion I want to answer a few questions upfront:

Q: Why wouldn't you stop cheaters from doing their dirty work!

A: And how could I prevent them? Drop the wrong code? One cheater would have checked it and written about it. Incorrect codes often appear in such groups.

Q: Do you have time during the contest to do this nonsense?

A: Well, usually the writers answer the questions. But when there weren't many questions, I did messaging. I apologize if I made anyone wait a long time for an answer to a question.

P.S. Do you think I should leave links to cheater groups/channels? I'll read the comments, and if this idea will be supported, I'll post the links.

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By Wind_Eagle, 9 months ago, In English

Will we, will you...
Can we, can you, can we change?

1562A - The Miracle and the Sleeper

Hint 1
Hint 2
Solution
Code C++ (Wind_Eagle)

1562B - Scenes From a Memory

Hint 1
Hint 2
Solution
Code C++ (Wind_Eagle)
Additional Problem 1
Solution of Additional Problem 1
Additional Problem 2
Solution of Additional Problem 2

1562C - Rings

Hint 1
Hint 2
Solution
Code C++ (Wind_Eagle)
Additional Problem 1
Solution of Additional Problem 1
Additional Problem 2
Solution of Additional Problem 2

1562D1 - Two Hundred Twenty One (easy version)

Hint 1
Hint 2
Hint 3
Solution
Code C++ (Wind_Eagle)

1562D2 - Two Hundred Twenty One (hard version)

Hints 1-3
Hint 4
Hint 5
Solution
Code C++ (Wind_Eagle)
Interesting question

1562E - Rescue Niwen!

Hint 1
Hint 2
Hint 3
Solution
Code C++ (Wind_Eagle)
Interesting question

1562F - Tubular Bells

Hint 1
Hint 2
Hint 3
Hint 4
Hint 5
Solution
Code C++ (Wind_Eagle)

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By Wind_Eagle, 9 months ago, In English

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: mhq, BigBag, IntoTheNight, Kuroni, programmer228, MagentaCobra, 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!

Winners
Some other people who deserve congratulations

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By Wind_Eagle, 20 months ago, translation, In English

Hello, Codeforces!

I am very glad to invite you to the Codeforces Round #672 (Div. 2), which will take place in Sep/24/2020 17:35 (Moscow time). This round will be rated for the participants with rating lower than 2100.

All tasks were made by me, but gepardo helped me a lot with the last two tasks, probably these tasks wouldn't have appeared if he didn't help me.

My thanks to:

You will have 2 hours for solving 5 tasks, one of which will be divided into easy and hard verions. I hope you will enjoy the round, I tried to make short statements and strong pretests interesting tasks.

Score distribution: 500 — 1000 — (1000 + 1250) — 2000 — 3000

UPD: The editorial is available. English version will be ready after the system testing is over.

UPD2: The english version of the editorial is ready.

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By Wind_Eagle, history, 20 months ago, translation, In English

Hello Codeforces! Recently I've become an author of a Codeforces Round #672 (Div. 2) (it will take place soon). Immedaitely after placing my contest in a timetable, I have been attacked by the messages of a following content:

"Hello, can I be a tester of your codeforces round? I want to gain experience in testing CF rounds" etc.

I want to tell you something. If you didn't know, the process of making and testing the round looks like this:

1) Author makes codeforces round. Of course, he/she also needs to test his/her round carefully.

2) When this work is done, round coordinator invites some people to test your round. Both author and coordinator can choose testers at this stage.

3) When testers looked through the round and did their work, round can be placed into the timetable. After this no testers required.

So, now, I hope, now you know that when contest is already done and scheduled, it makes no sense to write such messages to authors. By the way, this messages are not annoying. I just want you to not to waste your time.

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