Can someone please explain how to solve the problem http://codeforces.net/problemset/problem/453/B I am unable to understand even the editorials here http://codeforces.net/blog/entry/13190 that how not taking the factors of given array a[i] will minimise the expression like in editorials and operation is done to remove the prime factors of a[i] using bitmask.Also I wasn;t able to understand the dp part.So a detailed explanation will be highly appreciated. Thanks in advance.