Stone Game

Alice and Bob play the following game : There are N piles of stones with Si stones in the ith pile. Piles are numbered from 1 to N. Alice and Bob play alternately, with Alice starting. In a turn, the player chooses any pile i which has atleast i stones in it, and removes exactly i stones from it. The game ends when there is no such pile. The player who plays last wins the game. Assuming Alice and