Hello guys! I tried without succes to solve this gorgeous problem (http://codeforces.com/contest/587/problem/E). I looked after in the editorial and I still have some questions : What is really the basis of a vector and why the answer is always 1 << b.size() , where b = basis of the subsequence ? If you know the answers or you can offer me another solution to the problem, please help me :D Thanks in advance!