#include <stdio.h>
int fact(int n) {
  int r, i;
  r = 1;
  for (i = 1; i <= n; i++)
    r *= i;
  return r;
}

int main() {
  int n, r;
  printf("n = "); scanf("%d", &n);
  printf("r = "); scanf("%d", &r);
  printf("%dP%d = %d\n", n, r, fact(n) / fact(n - r));
  printf("%dC%d = %d\n", n, r, fact(n) / fact(r) / fact(n - r));
  return 0;
}
/* end */

Floating point exception