8
0   23  12  0  0  0  0  0
23  0   25  0  22  0  0  35
12  25  0   18  0  0  0  0
0  0  18  0   0  20  0  0
0  22  0  0  0   23  14  0
0  0  0  20  23  0   24  0
0  0  0  0  14  24  0   16
0  35  0  0  0  0  16  0
4