To those of you who tried "Olympiad and Contests Around the World-2", I'm really sorry!
There was a huge wording issue with one of the problems and it was completely my fault. I was careless and didn't check the problem-wordings properly. I apologize. It's been fixed.
I have gone through all the other problems right now and they seem okay. But if you see any more issues with the problems, do use the 'report' feature to let me know what's wrong with them.
Also, I have two solutions that are very different from the one posted for APMO Power. Can you think of one that uses infinite descent?