n = 8;
a = [| 0, 1, 0, 1, 0, 0, 0, 0
     | 0, 1, 0, 0, 0, 1, 0, 0
     | 0, 0, 0, 0, 0, 0, 0, 1
     | 0, 0, 0, 0, 1, 0, 0, 0
     | 0, 0, 0, 0, 0, 0, 0, 0
     | 1, 0, 0, 0, 0, 0, 1, 0
     | 1, 0, 0, 1, 0, 0, 0, 1
     | 0, 0, 0, 0, 1, 0, 0, 0
     |];

row_sums = [3, 1, 1, 0, 2, 1, 0, 4];
col_sums = [2, 2, 1, 1, 1, 2, 1, 2];