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);
}
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);
}