After competing today in Codeforces Round 620 (Div. 2), I received the following message from System:

Attention!

Your solution 71152328 for the problem 1304E significantly coincides with solutions ksun48/71134293, hoke_t/71152328, Venia/71156816, hanga97/71159069. 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://codeforces.net/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.

Clearly, these are all due to using the data structure LCA from the well-known KACTL library maintained largely by simonlindholm, Chilli, and many others, and was published online well before the beginning of the round (check the Git commit history). You can see that aryanc403, a tester for Codeforces Round 620 (Div. 2), used the exact same LCA code as well (71170167). MikeMirzayanov, can you please look at this incident and correct it by putting all of us back on the leaderboard and giving rating change? I had over +100 delta in the contest, and it's frankly quite disappointing that the system doesn't have a way to notice that such commonly used templates are not cheating (especially if round tester uses it too). I hope my monetary contribution to Codeforces this year can help prevent such incidents in the future.