$50
A+A, A+B, A+C, A+D, A+E, A+G, A+H, B+B, B+C, B+D, B+E, B+G, B+H, C+C, C+D, C+E, C+G, C+H, D+D, D+E, D+G, D+H, E+E, E+G, E+H, G+G, G+H, H+H
