Sometimes I work on a problem and figure out the majority of it, but I can't understand some truly difficult sections. as when I'm working on the Timus Problem Set. I become quite depressed over the fact that I can't solve the problem and that no one is even willing to assist me because I don't even have friends who are passionate about it and there isn't an editorial with a convincing explanation. what am I supposed to do and I even spend so much time on these problems.