### KAN's blog

By KAN, 3 weeks ago, translation,

Hello Codeforces.

Unfortunately a few hours after the end of Round #819 we were pointed out that one of the problems was stolen from another online judge.

Codeforces team strongly condemns such an action from the author. By no means is this acceptable behavior. This is the first and the most important rule of problem making: your problem should be new up to your best knowledge.

A lot of people put lots of effort into creation of every single round. You can find these people mentioned in the announcements and they indeed deserve these acknowledgments. And yet a single cowardly decision can ruin this huge work and experience of thousands of participants.

In this particular case the copied problem was not widely known, and it seems that this made little or no impact on the course of the round. Nevertheless, we stick to the decision that in such case the round cannot be considered successful, and thus no rating changes can be applied. We will also remove the problem from the round and from the problemset as well as blacklist the author.

We hope that this case will be a lesson for future authors and this situation does not repeat in the future.

• +872

 » 3 weeks ago, # |   +1 Can you share Which problem?
•  » » 3 weeks ago, # ^ |   +7 refer to this blog.
 » 3 weeks ago, # |   +262 Making the round unrated is unnecessary, IMO.
•  » » 3 weeks ago, # ^ |   +82 Agreed
•  » » 3 weeks ago, # ^ | ← Rev. 4 →   0 well, though I agree on this personally, there are still reasons to make this round unrated. I have seen many people suffer with F, both in the same room (room for hacks, not the physical room) and in the standings. Assume, in this situation, someone knew it was a stolen problem. In this case, they would have an unfair advantage! This unfair advantage is the exact reason to make this round unrated. While I am not a representative of Codeforces, I consider all such "unfair advantages" undesirable and therefore enough reason for making a round unrated.UPD: I understand both thoughts on either keeping the round rated or making the round unrated. However, as problemsetters, we (and by we I mean myself too, I prepare problems for other platforms) have many different values to pursue. These include fairness and justice. I hope you understand how this "unfair advantage" could be unjust and understand my idea as well.
•  » » » 3 weeks ago, # ^ |   +42 Do you think a round should be unrated if one of the problems was similar to a existing problem because of actual coincidence?
•  » » » » 3 weeks ago, # ^ |   +15 This is quite hard to decide. But really, no, in this case we can attribute the advantage to the luck and wisdom of the ones who found a similarity. Some problems can be similar, it happens. When this happens, we can say that these people who found a similarity are very wise, being able to find a connection of the problem they're solving to one they did some time ago. That is a skill, after all. However for stolen problems, there is no "skill factor" over this. (If Googling is a skill, then maybe there is, but imho it's really not) When two problems are exactly the same, people can just copy-paste one side's solution to the other. There is then no more thinking about it, they just copy-pasted, got AC, that's it. While I personally think removing duplicates "entirely" is impossible (problemsetters are humans after all), they at least need to try their best to find out duplicates as much as possible in the problemsetting process.
•  » » » » » 3 weeks ago, # ^ |   0 Ok, let me change the question. Do you think a round should be unrated if one of the problems was THE SAME AS a existing problem because of actual coincidence?
•  » » » » » » 3 weeks ago, # ^ | ← Rev. 3 →   0 Okay, if that's the case, then why not just make it unrated. We have some things to consider in this case though, such as 1. was it easy enough to find out the original problem? 2. did the coincidence give some participants an unfair advantage? 3. was the coincidence easily preventable? if 1 and 2 are true, then making it unrated should be a good decision. 3 though, is a hard question. there are tens of thousands of problems in the CP scene, if not millions. they should have tried their best in preventing coincidences, but as problemsetters are people, they can't review the massive amount of problems spread across different judges. if 3 is true, then the problemsetter may need a (weak) punishment, maybe a warning. but it's not an easy thing to simply say either 3 is true or not, after all detecting duplicates without the source problem in mind is hard.
•  » » » » 3 weeks ago, # ^ | ← Rev. 5 →   -13 They even copied sample cases that can not be a actual coincidence.Codeforces has set of rules to be follow . That's what happened.I fully agree with the decision of KAN.
•  » » 3 weeks ago, # ^ |   +14
•  » » 3 weeks ago, # ^ |   -45 Agreed strongly
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   -46 What about those who touched new color first time and rolled back?? Genuinely feeling bad for them.
•  » » » 3 weeks ago, # ^ | ← Rev. 2 →   -39 I am one of them:-( After a week i got the new color
•  » » » » 3 weeks ago, # ^ |   -39 Me too
•  » » » » » 3 weeks ago, # ^ | ← Rev. 2 →   -39 negative 1
•  » » » » » » 3 weeks ago, # ^ |   -39 plus 1
•  » » » » » » » 3 weeks ago, # ^ |   -39 plus 1
•  » » » » » » » » 3 weeks ago, # ^ |   -39 plus 1
•  » » » » » » » » » 3 weeks ago, # ^ |   -24 plus 1
•  » » » 3 weeks ago, # ^ |   -34 Plus 1
•  » » » 3 weeks ago, # ^ |   -22 It sucks man. It really sucks.
•  » » 3 weeks ago, # ^ |   -14 Agreed
 » 3 weeks ago, # |   -44 me after getting positive delta in the contest and getting rolled back:
•  » » 3 weeks ago, # ^ |   +5 +94 and the round is unrated, of course. It sucks, but ultimately I agree that there has to be a strong message sent out that plagiarism won't be tolerated for future problemsetters.
 » 3 weeks ago, # |   +149 Thanks for making this announcement. May I ask why you plan to remove the problem from the round/problemset when the same was not done for 1710E - Two Arrays?
•  » » 3 weeks ago, # ^ |   +70 Agreed: barring copyright concerns, it would be helpful to have the problem preserved so that e.g. the standings can be viewed as they were in the contest, the contest can be VCed, etc.
•  » » » 3 weeks ago, # ^ |   +73 I also think that removing the problem from contest/problemset is unnecessary.
•  » » » » 3 weeks ago, # ^ | ← Rev. 2 →   +38 The difference between this problem and other actual/notorious coincidences is that this time one of the dmoj staff wrote to coordinator Artyom123 expecting an appropriate action (against setters). Ig this is one of the reasons influencing the unavailability of this problem on codeforces. Spoilerhttps://dmoj.ca/ there is a discord link beside "comment stream"In #general they were discussing contacting Artyom123 about this.
•  » » » » » 3 weeks ago, # ^ |   +18 Could you provide an evidence that such a request happened? I don't think removing the problem from the round and problemset works as a punishment against the problem setter.
•  » » » » » » 3 weeks ago, # ^ |   +15 Join the server (the link is present in spoilers in the previous comment), open the general channel and scroll up to read the last ~100/200 msgs. They were discussing contacting Artyom123, and later, one of them wrote that Artyom123 had read the message. In the same server, you can also talk to their staff if you want to.
•  » » » » » » » 3 weeks ago, # ^ |   +10 I joined the sever and was able to verify that such a request did exist. Thank you very much. DMOJ staff just said "they expect appropriate action", not "please remove the problem from the round and problemset". It is up to Artyom (and KAN?) to decide what action they will take, so I don't think the DMOJ staffs can provide an explanation.
•  » » » » » » » » 3 weeks ago, # ^ |   +21 It's just a grey area (I'm not a lawyer, and CF and DMOJ have their licenses wrt to problems); probably that's what Artyom (and KAN?) want to avoid, even tho they may have not asked for it. I doubt at present Artyom (and KAN?) are going to revert back unless DMOJ staff explicitly says they don't have any problem wrt this problem being present on CF, after that people ask Artyom (and KAN?) again to add this problem back on CF. You can try going by this route if you care too much about this problem being available on CF.
 » 3 weeks ago, # |   +73 I do think this is a good decision, even if there was no impact, the behavior of the author should never be encouraged, and being unrated is also a warning to future authors.
•  » » 3 weeks ago, # ^ |   +37 Making the round unrated isn't important for the author who's copied the problem, Why should the rights of other authors and people who participated in the round be ruined?! Do you think it's fair?
 » 3 weeks ago, # |   +109 Nice. Next time when I drop ratings, I will connect my problem setter friend to make the round unrated.
 » 3 weeks ago, # |   0 my friend got about +90 and he became a specialist for the first time and he was planning to pay for me in a restaurant, you spoiled it for me, that's not fair guys
•  » » 3 weeks ago, # ^ |   +5 so do i,now i back to Pupil,what bad luck.
•  » » » 3 weeks ago, # ^ |   +5 me too :(
 » 3 weeks ago, # |   +29 It's not the first problem that was copied for the contest. Neither it affected heavily the standings. What's so special about it to revert rating changes for everybody?
•  » » 3 weeks ago, # ^ |   -26 last time it was a Div.1 and a Div.2 separately, this time it's a Combined round. probably that is why the only options were to make it rated for all or make it unrated for all, in which the former would have been undesirable (last time's Div.1 was unrated too)
•  » » » 3 weeks ago, # ^ |   -9 For those with low scores, they need to spend more energy and time to solve the first few easy problems in each game, but for them, the later problems have nothing to do with them , but they have something to do with them when they are leaked.Unrated is really fair?
•  » » » » 3 weeks ago, # ^ |   0 unfair? okay, maybe. but did they have a choice? maybe not. It's a combined round, meaning that their only choice was to rate all or unrate all. the former is unfair to people who solved F and the latter is unfair to the ones who did not get to that point. do you think they really had a choice?
•  » » » » » 3 weeks ago, # ^ | ← Rev. 2 →   -10 In your opinion, how should we deal with this theft next time? Won't stealing stop just because of one or two warnings, or do we only choose the round that can do most of the questions? The number of participants in the 1+2 competition is even lower than that in some div.2 competitions.
•  » » » » » » 3 weeks ago, # ^ |   0 If Codeforces had a way to recalculate the ratings with only the stolen problems excluded, that would be much better for the future.
 » 3 weeks ago, # | ← Rev. 2 →   +89 that's not fair we spent 135 minutes doing our best
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   -16 I agree your point
•  » » 3 weeks ago, # ^ |   0 yes yes, I totally agree with you
•  » » 3 weeks ago, # ^ |   -9 we made a great effort in this contest we want our money back
•  » » » 3 weeks ago, # ^ |   0 pardon me, you want whose money back?
•  » » » » 3 weeks ago, # ^ |   -19 it's an expression sentence meaning that we want our rates back. pay me some focus bro, my life is short:)
•  » » » » » 3 weeks ago, # ^ |   0 oh. I understand you fam, I lost rating due to this rollback too.
•  » » » 3 weeks ago, # ^ |   0 It's a shame we can't get our time back though.
•  » » 3 weeks ago, # ^ |   0 yes bro and I don't like it at all that they have reverted the ratings just because of a single person's fault
 » 3 weeks ago, # |   +8 If you do it so you need to do the same for CF1710E bro.
 » 3 weeks ago, # |   +3 What a pity.
 » 3 weeks ago, # |   +41 I'm sorry, but I think this is unfair. We spent a lot of time solving these problems and the first 3 were good problems. I get that this should be a message to future authors, but you said that it made little to no impact on the round. I also got Pupil for the first time ever, and now this happens.. I don't know what to say, but I'm not happy about that
 » 3 weeks ago, # |   +1 I wanted to participate in the contest, but skipped. When morning came, I heard the contest has become unrated? :/
 » 3 weeks ago, # |   +47 Please make it unrated next time when I drop rating, thx.
 » 3 weeks ago, # |   +17 Was not the first time.I think that codeforces should have some clear rules to curb such behavior.
 » 3 weeks ago, # |   +24 Making the round unrated is overkill in my opinion since so few people actually solved F. I hope this decision can be changed.
•  » » 3 weeks ago, # ^ |   +15 In ROUND810, div.2 also has the original question, and the result is still rated. This time there was unrated.
 » 3 weeks ago, # |   +18 So why the Codeforces Round #759 (Div. 2, based on Technocup 2022 Elimination Round 3) is rated?
•  » » 3 weeks ago, # ^ |   +8 Was there ever a conclusion reached that the problem was deliberately copied in that case? This seems to be the determining factor — coincidences can happen, but deliberate copying is forbidden.
•  » » » 3 weeks ago, # ^ |   -17 How do you think about my ideas about why this round is unrated and the difference between coincidence and theft? There's a lot of downvotes, but I have no idea on the reason except for "toxicity". I feel like basically this community upvotes on every comment who sympathize with their own loss and downvote the rest. For all people who don't consider diversity of thought and think only for themselves, I have only one thing to tell you, shame on you!
•  » » » » 3 weeks ago, # ^ |   +15 I feel like basically this community upvotes on every comment who sympathize with their own loss and downvote the rest. Yea this is common, I remember when I wrote comments about FBHC they were initially upvoted, but then later became downvoted, possibly by people who want FBHC to move to the "code runs on server" format. Hard to know though.
•  » » » » 3 weeks ago, # ^ |   0 I upvoted.
•  » » » 3 weeks ago, # ^ |   +5 You can see 1591F is just like ARC115E. But the round is still rated, though more people found.
•  » » » » 3 weeks ago, # ^ |   0 Was there ever a conclusion reached that the problem was deliberately copied in that case? This seems to be the determining factor — coincidences can happen, but deliberate copying is forbidden.
•  » » » » » 3 weeks ago, # ^ |   -23 Okay, you guys make the rules. You have the right to explain.
 » 3 weeks ago, # |   +21 I spent a lot of time solving this round, but when I was happy that I was about to get promoted, you told me not to rate it. Although I can only solving A、B、C, it is obvious that not many people can solve F questions.
 » 3 weeks ago, # |   +32 I thought you were deleting the cheaters and i will get my rating back but this time the author is cheating
 » 3 weeks ago, # |   0 oh no
 » 3 weeks ago, # | ← Rev. 3 →   -13 Ok here's another idea. I went through the submissions and F was only solved by reds and a handful of Masters. So why not remove F from the contest and recalculate the scores, or just make it unrated for Div 1 like #810. You are taking away a good contest from 95% of the participants who worked hard trying to solve A-B-C.
 » 3 weeks ago, # |   +19 me after getting bad delta
 » 3 weeks ago, # |   +10 I got +13 this time but I think this decision is perfectly valid. In order to make a completely fair decision from the perspective of the administrator, it is necessary to consider even participants who wasted time due to problem F and could not focus more on other problems. This is literally impossible.
 » 3 weeks ago, # |   +51 I participated in the contest with $102^{\circ}F$ fever, and now it has become unrated...
•  » » 3 weeks ago, # ^ |   0 upvoted in wishes for your recovery. by recovery I mean both rating and health!
 » 3 weeks ago, # |   -10 please don't make the round unrated just remove the problem and its points plz :( :( :(
 » 3 weeks ago, # |   +6 Only a little participants solved the problem F,making the round unrated is unfair for other participants
 » 3 weeks ago, # |   +15 Current state of codeforces after this blog.
 » 3 weeks ago, # |   +18 For those who are upset about the round being unrated, please appreciate the experience you had with all the other problems. The rating is just a number that simply estimates your ability, and having one or two unrated rounds wouldn't have much impact on its accuracy. But the real value for the contest is on the problem-solving experience, honing your skill and reasoning ability as you worked through a problem (even if it was the copied problem) and tried to implement a solution. None of this is being affected by having this round unrated. While it's unfortunate that your efforts aren't reflected in your rating, this does not, in any way, erase the actual experience of the contest and its corresponding benefits.
 » 3 weeks ago, # |   +2 I just got Specialist last night,now back to Pupil
 » 3 weeks ago, # |   -19 Sometimes there are people who have done immense hard work in the contest. So you cannot turn a blind eye and make the contest unrated like it was nothing. At least the ones who didn't cheat should get their rights.
 » 3 weeks ago, # | ← Rev. 2 →   0 Well I see the necessity in delivering a message to future authors in creating original problems. But when I saw myself being +126 on CF predictor and the round being unrated, I can't help myself being frustrated and well, pissed off
 » 3 weeks ago, # |   -17 Woke up to my +150 rating gone, actually gonna commit
 » 3 weeks ago, # |   -36 I know this may sound dumb but why not make the problem that was copied and every problem after that problem unrated. Say the contest has 7 problems and problem number 5 was copied then what if Codeforces just ignores problem number 5,6,7 and give the ratings on the basis of first 4 problems as if the problem number 5,6,7 doesn't exist. I know many will think why to make 6th problem and 7th problem unrated but you see some people will give more time and effort on the 5th problem than the people who knew that the problem was copied and they will quickly complete problem number 5 and move on to the next question which will give "unfair advantage" to those who knew the problem was copied. I know this solution is a bit stupid but it's still better than robbing the beginners who missed a very important Indian festival to give a Codeforces contest and solved A in 4 attempts B in 4 attempts got a positive delta of 47 had nothing to do with the copied problem but still the contest was unrated for him.
 » 3 weeks ago, # |   0 As usual, I did well in the contest and now it's made unrated :((
 » 3 weeks ago, # |   -7 Dont make this contest unrated..
•  » » 3 weeks ago, # ^ |   -9 Dont make this cintest unrated
 » 3 weeks ago, # |   +3 If you make a round unrated only for one copied problem (Which didn't affect someone else's rank as mentioned in the blog), Then you should do it for another rounds too, You could make rounds 805 and 808 unrated too but you didn't, That's unfair, Also IMO making this round unrated wasn't necessary, Hope asap codeforces becomes real codeforces not googleforces.
 » 3 weeks ago, # |   0 This is unfair. We spent 2 hours and 15 minutes to solve these problems. Now this round of contest has been unrated. This is not a punishment for the author but for the participants.
 » 3 weeks ago, # |   -17 Only a few people solved the problem!! Don't make the contest unrated rather punish the author of the problem.
 » 3 weeks ago, # |   -8 Woah got+101 in this contest and now it's unrated. Hard luck. I didn't quite get what's the point behind making it unrated.
 » 3 weeks ago, # |   0 Good decision for everyone. But thanks for other problems.
 » 3 weeks ago, # |   -8 So I get to reach my max rating with a 105+ in this contest and then wake up in the morning to see this? (sighs...)
 » 3 weeks ago, # |   +49 I support making it unrated, but why remove the problem? This would ruin the standings and make contestents lose their submissions.
•  » » 3 weeks ago, # ^ |   0 I suggest removing problem E in last round but not this time because the impact on this problem is smaller, as the majority of contestants who passed this problem haven't seen this problem before.
 » 3 weeks ago, # |   0 Is there any punishment to the fake author themselves? in my opinion stealing a problem intentionally is worse than cheating
 » 3 weeks ago, # |   -11 This was my best performance in CF , solved 3 problems and got +223 rating and now it's unrated .....Bad luck ig.. Is it really necessary to make this round unrated ? Most contestants didn't even reached the problem statement of F.
 » 3 weeks ago, # |   +1 Imo this was way too unnecessary and disheartening.
 » 3 weeks ago, # |   0 Not very related to the above topic but I want to ask about problem A: What will happen to this statement if n = 1? *max_element (a + 2, a + 1 + n); Thank.171076641 Wrong answer on test 23 *max_element (a + 2, a + 1 + n);171158888 Accepted (n==1 ? 0 : *max_element(a+2, a+1+n) - a[1]);
•  » » 3 weeks ago, # ^ |   0 Because if n is 1 then that function goes range out(if I am not mistaken)
 » 3 weeks ago, # |   +16 Please make this round rated.Making this round unrated would be a punishment for the participants.Out of 10000+ participants just 50+ have solved that problem and also most of them were red or orange.
•  » » 3 weeks ago, # ^ |   -9 So orange or red participants are not participants? Only you guy the green participant is participant?
•  » » » 3 weeks ago, # ^ |   +2 No I mean they are most probably authentic people which implies the problems were most probably not cheated.
•  » » » » 3 weeks ago, # ^ |   0 The problem is surely cheated and the person is surely authentic.
 » 3 weeks ago, # |   0 Approx 50 people solved F. Making this round unrated is just unfair for almost everyone who participated in this contest. This actually seems to be a punishment for participants rather than author. Can't we just remove the problem F, this way it will have much lesser impact.
 » 3 weeks ago, # |   +1 Wtf, that's not fair
 » 3 weeks ago, # |   +16 So disappointed. This round had great problems in my opinion. It's unfortunate that the hard work of the problem authors has been diminished.
 » 3 weeks ago, # |   +60 Rated div.1 contests are too rare nowadays, and on top of it, this happens.
•  » » 3 weeks ago, # ^ |   0 can you explain why they are rare ?are they running out of ideas for new problems or because the majority are in div2,3 so they don't focus on div1
•  » » » 3 weeks ago, # ^ |   +12 Finding ideas for hard problems is difficult.
 » 3 weeks ago, # | ← Rev. 2 →   +12 We will also remove the problem from the round and from the problemset as well as blacklist the author. Could you explain why this has to be done as it seems like multiple people are against it? KAN
•  » » 3 weeks ago, # ^ |   +34 Pretty sure it is a violation of DMOJ terms of service by the author, assuming we include in material the intellectual property rights of those authors. You may not host material the DMOJ: Modern Online Judge owns on any website with online grading capabilities (without our consent). But that's not even the main issue I would say, do we really want to see the platform become a host of stolen problems, one where thieves get to rejoice at all the oblivious upsolvers years from now solving the problem while overlooking the fact it was copied? Deleting is the way to make it clear that any effort put into preparing stolen problems it will be wasted and thrown way once exposed, especially since legal recourse is pretty much infeasible.I suppose one could argue for a message in the statement exposing the event with a reference to the original source.In fact, I don't quite understand why the last copied problem has not been deleted as well along with this one. I feel like the same rationale should apply...
•  » » » 3 weeks ago, # ^ |   +8 I suppose one could argue for a message in the statement exposing the event with a reference to the original source. I think this will be a good idea.
•  » » » 3 weeks ago, # ^ | ← Rev. 5 →   0 The "Two Arrays" problem, as far as I recall, was copied from a source (Bytedance Grand Prix) which wasn't publicly available (or perhaps was but not in English) at the time of the contest (and it was also noted that a disproportionate number of in-contest solves were from people in China). I have been informed that there now currently exists a public online judge mirror here, but the user interface is all in Korean. (You can still kinda blunder your way through registration and submission by Google Translate and/or using the URLs as hints, but as a non-Korean-speaker I consider this a significantly less usable experience than DMOJ)
 » 3 weeks ago, # |   -38 KAN Sir as people are heartily requesting to make this contest rated, I would like to suggest you one thing. Remove this problem from the contest.. and just give ratings based on the other problems all of us have solved.
•  » » 3 weeks ago, # ^ |   0 Stfu cheater
•  » » » 3 weeks ago, # ^ |   -16 xD roasted lmao
•  » » 3 weeks ago, # ^ |   +39 Calculating the score just based on the other problems does not work. During the contest, participants try their best to score as much as possible in the given set of problems. This often includes strategies like looking at the standings, skipping problems that seem difficult, etc. The removal of one problem can change participants' strategies significantly.I am good at data structure problems, so I often skip an adhoc-looking problem and try to solve a data structure problem. If after the contest it was decided that the data structure problem will be removed and ratings will be recalculated based on the score of other problems, I will feel that it is very unfair.
•  » » » 3 weeks ago, # ^ |   0 I'd like to know what you think will help solve this problem. After all, this competition has consumed too much energy.
•  » » » » 3 weeks ago, # ^ |   0 I think just having the contest be unrated is fine.
•  » » » » » 3 weeks ago, # ^ |   +3 What do you think if you count the people below 1900 who can't write F questions as div.2?
•  » » » » » » 3 weeks ago, # ^ |   0 What do you mean by "can't write F questions as div.2"?
•  » » » » » » » 3 weeks ago, # ^ |   +3 Sorry, there is something wrong with my expression. I mean, people with scores less than 1900 can't solve the F problem. So, can we say that most people with lower scores don't feel unfair? Then, can this group of people's achievements be regarded as a div.2 competition?
 » 3 weeks ago, # |   -44 KAN 50 or so people solved F, those too mostly reputable folks, so making the round unrated is harsh on the 10000+ people who actually sat for hours last night. Blacklist the author, mark the problem or anything else, but please dont make this unrated it is really really disheartening for all of us.
•  » » 3 weeks ago, # ^ |   -24 YES KAN please make round rated as problem F has not affected the contest that much.
•  » » 3 weeks ago, # ^ |   0 Exactly. I got to Pupil for the first time ever this contest and now I'm back to grey. It's unfair to make the round unrated for 10000+ participants when only 50 of them solved the copied problem. Please consider returning rating changes for everyone KAN
 » 3 weeks ago, # | ← Rev. 2 →   -8 .
 » 3 weeks ago, # | ← Rev. 2 →   -14 It's ridiculous that the author didn't dare to go online, admit this behavior and apologise to the public. This is something that deserves our despise most.
 » 3 weeks ago, # |   0 It has happened again.
 » 3 weeks ago, # | ← Rev. 4 →   -25 No, it's generally a strange situation, to be honest. If then (Codeforces Round #810 (Div. 1)) the Chinese contestants directly knew the solution and it was clearly visible that the stolen task had a strong influence on the results, then here is the task of 2017 from some super unpopular resource, where it was solved by one and a half people. In general, what are the probabilities that at least one of those who solved the problem then participated in this contest, and even remembers when and where exactly he solved it 5 years ago? I don't see anything wrong with making the task public. Apparently, the author thought the same and I agree with him. But the community, as usual, came up with a problem and unrated the contest for themselves, and now they are dissatisfiedDont get me wrong. Its not about "i ve got positive delta — i am maaad now". Its all about undeserved hatred towards the author
 » 3 weeks ago, # |   +14 On both of my last 2 div1 rounds I had plus delta, and both of them were made unrated. In round 810 plagiarism had a strong impact, but this time the impact is NONE. I think you should not make this round unrated. And if you do, I think you should permanently unrate all of div1 rounds from this day.
•  » » 3 weeks ago, # ^ |   0 No I think it should. It will serve as a warning to future problemsetters.
•  » » » 3 weeks ago, # ^ |   0 The warning will not involve the time and energy cost of so many people. :)
 » 3 weeks ago, # |   +50 If this round is rated, it will be my first time to get Master. I can say I've been waiting for this day for five years. But the reality gave me a big blow.Just for one problem, the contest is unrated. I think it's unfair for the 13,101 people who didn't solved this problem. And the most of us, even didn't reach that problem statement. This means that most people's efforts throughout the night are in vain. Additionally, I think the testers for this round also need to take some responsibility. This could have been avoided during testing, rather than announced it's unrated after the round. And throughout, the author little_angel didn't come out and give us an apology.I cannot accept such a decision. I sincerely hope that this round will be rated again, KAN. Thank you.
•  » » 3 weeks ago, # ^ |   0 Agreed. Maybe you should figure out some way of distributing the ratings but atleast don't be unfair with those who burnt their midnight oil to reach this point.
•  » » 3 weeks ago, # ^ |   +14 As I see it's unrated not because some people solved it, but because this has a bad effect on the image of Codeforces.
 » 3 weeks ago, # |   0 Well, negatively negative delta this time :DSorry for ones who now has negatively positive delta D:
 » 3 weeks ago, # |   +25 Lucky day for everyone with negative delta
•  » » 3 weeks ago, # ^ |   +1 I lost 70 points this round. I think im the most lucky contestant this round.
 » 3 weeks ago, # |   0 I feel that I'm so lucky because I will drop 100+ rating if this contest is rated.
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   0 Meanwhile me who lost 150+ rating T_T.
•  » » » 3 weeks ago, # ^ |   0 Hope you have good luck next contest
 » 3 weeks ago, # |   0 Amazing...
 » 3 weeks ago, # |   0 Why aren't such problems rejected in first place when rounds are being prepared/coordinated?
•  » » 3 weeks ago, # ^ |   +14 Finding out if a problem is a copy is very difficult and you can't avoid it completely.
 » 3 weeks ago, # |   0 Just blacklist the authors and let the rating changes stay please. People worked hard on those problems and deserve some +ve delta
 » 3 weeks ago, # | ← Rev. 2 →   +4 Maybe there is an option for this kind of 'mixed' round situations?Like, I'm not sure how possible this is, but my idea is to split it 'manually'. The last time this happened it was separated Div2-1 rounds. Later only Div1 was declared unrated since they weren't merged and the problem effect in Div2 was too brief.Maybe in Div1+2 rounds you can split participants into 2 groups? Like it would have been for normal div2 and div1 rounds — Users with rating lower than 1900 remain rated and their scores are calculated separately from those with rating>=1900. For those with rating 1900 or more round can be declared unrated. I'm not sure how fair this is, but it probably is a lil 'fairer' than declaring round unrated for a problem F which was solved by 110 by now and probably even less on contest(not sure). Some people might have wasted time on it, but those most likely were 1900+ and they won't be affected either way.Just an idea which might work, dunno.
•  » » 3 weeks ago, # ^ |   0 It seems that this idea should be reasonable, the number of people who score more than 1900 is not large, and it is almost impossible to write F with a score below 1900
•  » » 3 weeks ago, # ^ |   +10 I think the solution is to stop making combined rounds.
•  » » » 3 weeks ago, # ^ |   0 Might be, but combined rounds are quite a good way to shift from div2 to div1.I have never been in this situation but I envision shifting from Candidate Master to Master to be hard, since the only div option you got is Div1, where the best of CF gather together. You can participate in Div1 from 1900 but well, not sure, I haven't been there yet.
•  » » » » 3 weeks ago, # ^ |   +11 As a CM you also get to participate in Div. 2 rounds if there is no Div. 1 round at the same time. Anyway I wouldn't worry about such things. Either you have the skills to reliably get to and stay in Master or you don't.
•  » » » » » 3 weeks ago, # ^ |   0 Might be true, can't argue since I have never been there.
 » 3 weeks ago, # | ← Rev. 2 →   -14 g
 » 3 weeks ago, # | ← Rev. 2 →   -25 h
 » 3 weeks ago, # |   -10 This is unfair TT. For the thousands of people who are working their way up in competitive programming and don't even attempt F it's pretty harsh. Feels sad :(. Hope this doesn't happen again
 » 3 weeks ago, # | ← Rev. 2 →   -30 TOTALLY DISAGREE. this is unfair for the participants who just wasted two hours and more. there must be a compensation and appreciation for there time though it is not their problem.
 » 3 weeks ago, # |   -27 RATE THE CONTEST BBBBAAAAAAACKKKKKKKKKK!!!!!!!
 » 3 weeks ago, # |   +19 It's problem setter's fault, why unrated contestants?
•  » » 3 weeks ago, # ^ |   0 totally agree
•  » » 3 weeks ago, # ^ |   0 I feel like this is a punishment to 10000 participants who did their best, just because a lazy author copied a problem only about 50 people solved during the contest. I got to enjoy being Pupil for the first time for a few hours I guess. But I'm disappointed enough to feel unmotivated about future contests.
 » 3 weeks ago, # | ← Rev. 3 →   +4 It's not fair. Please make the round rated again. Very few people only solved problem 'F'. Try to understand the situation of others who gave their best effort around 2 hour 15 minute.
 » 3 weeks ago, # |   0 Out of curiosity, what would've been my rating change if everything was normal? I didn't check CF before rollback since I was just competing while working (so I assume it'd be rating loss) and last time I used rating predictor browser extension, it wasn't very accurate. Is there a reliable way to find out?
•  » » 3 weeks ago, # ^ |   +10 I use this sometimes, it's not very accurate, but gives you an idea. It usually displays a little lower gain than you would have actually got.F.E: the last time I used to check it, I got +137(in actuality, on CF) and the app displayed +(~110) or something similar.
•  » » 3 weeks ago, # ^ |   +10 I believe this is pretty accurate.
•  » » 3 weeks ago, # ^ |   +10 -63 by cf-predictor
 » 3 weeks ago, # |   +9 No need to make round Unrated
 » 3 weeks ago, # |   +1 All the participants with positive delta getting punishment for author's fault. Not Fair!
 » 3 weeks ago, # |   +2 This had little to none impact on the contest, making it unrated is more punishing for those who worked hard to improve their ranking than for the one who committed the theft. It's unfair and i hope you will reconsider your decision.
•  » » 3 weeks ago, # ^ |   0 I agree, this is the reason I won't do any CF rounds anymore in the future.
 » 3 weeks ago, # | ← Rev. 4 →   -8 g
 » 3 weeks ago, # |   +24 kotatsugame was becoming LGM for the first time. I feel bad for what happened :( Hope you will reach LGM soon.
•  » » 3 weeks ago, # ^ |   +66 Thank you for mentioning! I will continue to participant in contests as much as possible and do my best.
 » 3 weeks ago, # |   +1 I work for ten hours and then do cp just for rating. if I want skills, I can solve the problem on weekend. It's really a waste of time that the round become unrate. Doing cp then I only have 5 hours to sleep at night because of the work. It's totally no sense that someone said rating is not important.
 » 3 weeks ago, # | ← Rev. 2 →   +3 As a pupilI couldn't even reach the problem which was copied
 » 3 weeks ago, # | ← Rev. 2 →   -12 This contest should be rated. Because every contest is slightly unfair.In each contest I find some solution publicly before the contest ended. If the problem setter made a mistake, then why contestant will suffer? Only about 100 people submitted the solution. I think most of them have solved it fairly. This will not be a lesson for future authors because few weeks ago same thing happened on CF and the sufferers are contestants. I hope, if the same thing happen in future contest and then it would be rated.
 » 3 weeks ago, # |   +1 This way you punch us the author don't care about rating change ಥ⁠‿⁠ಥ
 » 3 weeks ago, # |   -16 It's not fair. Please make the round rated again. Very few people only solved problem 'F'. Try to understand the situation of others who gave their best effort around 2 hour 15 minute.
 » 3 weeks ago, # |   -9 unfair contest. dont know why you would even want to participate in this.guys, if you care about your rating, i'd avoid this one.
 » 3 weeks ago, # | ← Rev. 2 →   +14 Why so many people care about their rating? You should solve CF contests for practice or/and for fun, not for rating.
•  » » 3 weeks ago, # ^ |   +61 says the guy who hasn't done a contest in 2 years to preserve his shiny yellow color.
•  » » » 3 weeks ago, # ^ | ← Rev. 2 →   0 This is a coincidence :) I have left CP (atleast, solving, I'm still a problemsetter) right after May, 2020.
•  » » 3 weeks ago, # ^ | ← Rev. 5 →   +118 For people in GMT+8, the contest runs from 1035pm to 1250am. Many people in east asian time zones have to purposely change their sleep schedules or endure 4 hours sleep to compete in contests. As others have pointed out, if you only care about practice, then virtual contests are same, if not better because I can compete at a better time.Personally, this is why I compete so rarely on CF because I have to wait for term breaks to purposely shift my sleep schedule to something closer to MSK so that my brain will work in the middle of the night.That said, although I am obviously unhappy about losing LGM, I support the decision to unrate the round.
•  » » » 3 weeks ago, # ^ |   +8 Staying up all night really makes me tired, and the score is a part of my motivation.
•  » » » 3 weeks ago, # ^ |   +9 Never thought about it, makes sense now. Thanks!
•  » » 3 weeks ago, # ^ |   0 I set a small goal of 1400 points. In more than two months, the change of scores gave me the motivation to move forward. Although I was only green, I didn't miss a game. I'm not afraid of losing points, but I'm afraid I can't see my own changes. Now after this competition, I fantasize about the improvement of scores and the possibility of reaching 1400 points tomorrow. unrate, where a small number of talents are affected, is unacceptable to me.
•  » » 3 weeks ago, # ^ |   +13 Rating is what gives me the most fun
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   +16 it seems you never wrote div2 round while being 2100+, contest is still not easy for you and should be fun on paper, but on practise it's not the same feeling as a rated round, there's much less fun when you know round is unrated for you.
 » 3 weeks ago, # | ← Rev. 2 →   0 UnRated :(