for (int c0 = 1; c0 <= 18; c0 += 1)

  for (int c1 = 1; c1 <= 9; c1 += 1) {

    if (c0 % 2 == 0)

      s0(c1, c0 / 2);

    if (c0 <= 9)

      s1(c1, c0);

  }