Let B be an n times n chessboard, where n is a power of 2. Use a divide-and-conquer argument to describe (in words) how to cover all squares of B except one with L-shaped tiles. For example, if n = 2, then there are four squares three of which can be covered by one L-shaped tile, and if n = 4, then there are 16 squares of which 15 can be covered by 5 L-shaped tiles