Hey MikeMirzayanov, you have created an awesome platform helpful for both newbie and advanced coders. But some people are playing foul game for high ratings. I know the plagiarism detector cannot be 100% accurate but it can be improved to detect some of the "similar" codes. For example I found two users who are constantly cheating in each contest. These users are kunnu96 and ace_pocket .

So now we can close the topic as the guy has apologised. the official apology link is http://mirror.codeforces.com/blog/entry/48873?#comment-329747

Example in contest #383

for problem D: http://mirror.codeforces.com/contest/742/submission/22757394 http://mirror.codeforces.com/contest/742/submission/22751809

for problem C: http://mirror.codeforces.com/contest/742/submission/22747112 http://mirror.codeforces.com/contest/742/submission/22743090

Contest #366

for problem C: http://mirror.codeforces.com/contest/705/submission/19700112 http://mirror.codeforces.com/contest/705/submission/19703627

Contest #361

for problem C: http://mirror.codeforces.com/contest/689/submission/18926480 http://mirror.codeforces.com/contest/689/submission/18934160

I can go on but i think i have made my point. And the craziest part is how these people take out time to change code in a 2 hour contest. How to discourage the fraud is upto you. P.S. There are lot more people than these two and I will write about them too. Until then happy coding :)