/*
AizuOnline A0019
Factorial
*/
#include <stdio.h>

unsigned long long int fact(long int n)
{
  if (n == 0)
    return(1);
  else
    return(n * fact(n-1));
}



main()
{
long int n;

scanf("%ld",&n);

  printf("%lu\n",fact(n));

return(0);
}