1 for (int c1 = 1; c1 <= M; c1 += 1)
2   S1(0, c1);
3 for (int c0 = 1; c0 <= N; c0 += 1)
4   for (int c1 = 1; c1 <= M; c1 += 1)
5     S2(c0, c1);
6