if (M >= 2 && N >= 3)

  for (int c0 = 2; c0 < O; c0 += 1) {

    for (int c2 = 2; c2 <= M; c2 += 1)

      S1(c0, 2, c2);

    for (int c1 = 3; c1 < N; c1 += 1) {

      for (int c2 = 2; c2 <= M; c2 += 1)

        S2(c0, c1 - 1, c2);

      if (M >= 3)

        S4(c0, c1 - 1, 2);

      for (int c2 = 2; c2 < M - 1; c2 += 1) {

        S3(c0, c1 - 1, c2);

        S5(c0, c1 - 1, c2);

        S4(c0, c1 - 1, c2 + 1);

      }

      if (M >= 3) {

        S3(c0, c1 - 1, M - 1);

        S5(c0, c1 - 1, M - 1);

      }

      for (int c2 = 2; c2 <= M; c2 += 1)

        S1(c0, c1, c2);

    }

    for (int c2 = 2; c2 <= M; c2 += 1)

      S2(c0, N - 1, c2);

    if (M >= 3)

      S4(c0, N - 1, 2);

    for (int c2 = 2; c2 < M - 1; c2 += 1) {

      S3(c0, N - 1, c2);

      S5(c0, N - 1, c2);

      S4(c0, N - 1, c2 + 1);

    }

    if (M >= 3) {

      S3(c0, N - 1, M - 1);

      S5(c0, N - 1, M - 1);

    }

  }