Recently I saw this question on my quora feed. This question I think is primarily for someone who have won medals in IMO or any regional mathematics olympiad. Though it is open for everyone who are good in mathematics. I know some of our fellow codeforces users who are winner of previous IMO likes of [user:rng_58,2016-11-28],[user:Swistakk,2016-11-28],[user:Xellos,2016-11-28],[user:hos.lyric,2016-11-28], etc. So their view would be quite helpful specially [user:rng_58,2016-11-28] has written a [blog](http://mirror.codeforces.com/blog/rng_58entry/19326) regarding very nice IMO final problem.