/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
#include <stdio.h>
#include <stdlib.h>

int factorial(int);

int main(int argc, char *argv[])
{
  printf("%d\n", factorial(atoi(argv[1])));
  return 0;
}

int factorial(int N)
  {
    if (N == 0) return 1;
    return N*factorial(N-1);
  }