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);
}