Grid Game

Alice and Bob is playing a game with stones. There is a NxN grid in each cell there may be a stone or may be empty cell. If a cell contain '.' (without single quotes) it means its an empty cell and if it contains 'S' (it means it has a stone). Alice and Bob alternatively and optimally Play a game The game rules are as follows: 1) A player move some stones from the grid. He / She can remove st