(b << 8)

((b << 8) | c))

((a << 16) | ((b << 8) | c))

r1 = (merged & 0x00003F);

r1 = ((merged >> 0)  & 0x3F);
r2 = ((merged >> 6)  & 0x3F);
r3 = ((merged >> 12) & 0x3F);
r4 = ((merged >> 18) & 0x3F);

char /*or int*/ a, b, c;
int merged, r1, r2, r3, r4;

scanf(" %c %c %c", &a, &b, &c);

merged = ((a << 16) | ((b << 8) | c));

r1 = ((merged >> 0)  & 0x3F);
r2 = ((merged >> 6)  & 0x3F);
r3 = ((merged >> 12) & 0x3F);
r4 = ((merged >> 18) & 0x3F);

printf("%d %d %d %dn", r1, r2, r3, r4);