{
  S3(1, 1);
  for (int c0 = 2; c0 <= M; c0 += 1) {
    S1(c0, 1);
    for (int c1 = 2; c1 < c0; c1 += 1)
      S2(c0, c1);
    S4(c0, c0);
  }
}