{
  for (int c1 = 1; c1 <= M; c1 += 1)
    S1(0, c1);
  for (int c0 = 1; c0 <= N; c0 += 1)
    for (int c1 = 1; c1 <= M; c1 += 1)
      S2(c0, c1);
}