I've joined Codeforces 4 months ago. The first goal I set for myself is becoming a blue coder. But after I've taken part in some contests I found it's not so easy. I've taken part in 9 contests and my current rating is 1363. In Div.2 contests I can averagely solve 2 problem. But I sometimes haven't got any ideas for problem C! And when I'm analyasing how some of my friends (tzc_wk, i_wanna_bao0_pj) became blue, I found that they have one thing in common: they all have the ability to solve Div.2C. So it seems that to become blue I should have the ability to solve Div.2C. But what problems should I do? With what level of difficulty? What kind of algorithm? Greedy, graphs, DP, math or something else? I'm really confused.