#include<stdio.h>

int fact(int n)
{
   int i;
   int result = 1;

   for (i=1; i<=n; i++)
      result *= i;

   return result;
}

int main(int argc, char **argv)
{
   if (argc > 1) {
      int n = atoi(argv[1]);
      printf("The factorial of %d is %d\n", n, fact(n));
      return 0;
   }
   else {
      puts("Please specify a number.");
      return -1;
   }
}