why?!? u might be asking, well... because if u know advanced math, when u open a math problem u just need to think and KABOOM, u solved it in less than 10 minutes! also because most problem (ABC & ABCD) in div 2 and 3 are math problems. for beginners (like me) u should start by working on algebra, combinatorics, and number theory problems numbered 1-5 on the AIME. it really helped me.