for (int c0 = 2; c0 <= 8; c0 += 2) {
  if ((c0 + 2) % 4 == 0) {
    for (int c1 = 1; c1 <= 9; c1 += 1)
      s1(c1, c0);
  } else {
    for (int c1 = 1; c1 <= 9; c1 += 1) {
      s0(c1, c0);
      s1(c1, c0);
    }
  }
}