Attention!

Your solution 221115308 for the problem 1863C significantly coincides with solutions Schi2oid/221115308, LBRhhhh/221122939. Such a coincidence is a clear rules violation. Note that unintentional leakage is also a violation. For example, do not use ideone.com with the default settings (public access to your code). If you have conclusive evidence that a coincidence has occurred due to the use of a common source published before the competition, write a comment to post about the round with all the details. More information can be found at http://mirror.codeforces.com/blog/entry/8790. Such violation of the rules may be the reason for blocking your account or other penalties. In case of repeated violations, your account may be blocked.

I received this surprising message today. I don't know who is LBRhhhh, and I didn't use any online IDE. In fact, this is a quite easy problem as C for Div.2, I just use the trick of "Back in time"(in China, we call it this way), use the result to get the beginning situation. I'm sure there's no chance LBRhhhh can get my code, unless there is a system vulnerability. I don't know what should I do to avoid the penalty. Please check this blog MikeMirzayanov.