Last Educational Round I solved 6/7 problems, but one of the problems 911G - Mass Change Queries got hacked in the 24h hacking period. Since then I tried to fix the solution and submitted it a few times, but still had no luck.

The bug on Codeforces is, that it shows the problem incorrectly as solved. On the PROBLEMSET page, the problem has a green background. And on the CONTESTS page it shows: Solved: 6 out of 7 (although it should be 5 out of 7). Only on the contest page itself Educational Codeforces Round 35 (Rated for Div. 2) the problem is correctly colored with red.