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 rng_58,Swistakk,Xellos,hos.lyric, etc. So their view would be quite helpful specially rng_58 has written a blog regarding very nice IMO final problem.