Can anyone please help me explaining the solution of this problem? I don't know how to solve this problem. Statement: We have a grid with H rows and W columns, Iroha is now standing in the top-left cell. She will repeat going right or down to the adjacent cell, until she reaches the bottom-right cell.But she cannot enter the cells in the intersection of the bottom A rows and the leftmost B columns(that is there are A x B forbidden cells).Find the number of ways she can travel to the bottom-right cell. Problem Link