Grid Coloring I

You are given an n\times m grid where each cell contains one character A, B, C or D. For each cell, you must change the character to A, B, C or D. The new character must be different from the old one. Your task is to change the characters in every cell such that no two adjacent cells have the same character. Input The first line has two integers n and m: the number of rows and columns. The ne