Well, it's my first time posting this type of blog on codeforces. Most of the time I could either find help elsewhere or find the answer myself, but this time it was different. I could not find any resource related to this problem, given that the discussion page for this Opencup contest is a blank russian blog from 2015 that I do not want to necropost on, and I do not know anyone who has solved this problem personally. The problem is here on Baekjoon OJ, and I would like to share my approach so far before asking the question, so that we can improve over the current approach.
Now here's the issue: I am still getting a WA verdict on the problem. This might mean that I need to prove a tighter bound possible, however I am unable to improve it further than the current status of the approach. Can anyone help me on this problem? Is there anyone here who have solved this problem personally and/or during the contest?