http://mirror.codeforces.com/problemset/problem/437/D i was trying this problem but i dont know why i am getting wrong answer on test 7.. my code outputs some negative value(maybe an overflow error but i checked and wasnt able to found one). please someone look through my code and help.. my submission :- http://mirror.codeforces.com/contest/437/submission/18170970 PS:- i matched my solution with some accepted one and my logic is same.