1 for (int c0 = 1; c0 <= M; c0 += 1)
2   for (int c1 = 1; c1 <= M; c1 += 1)
3     S1(c0, c1);
4 for (int c0 = 1; c0 <= M; c0 += 1)
5   for (int c1 = 1; c1 <= M; c1 += 1)
6     S2(c0, c1);
7