Many times I really stuck on a simple div 2 a level problem. I am approcahing it but not on the right way. I am building such a logic that is not related to it and I can not feel it. I am thinking it should be accepted and also on b level problem many times I can not build the logic if I do after the contest I saw that It was not the approach..what should I do..should I solve atcoder problem to get rid up to it or cses or cf a,b level.