Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120
#include <stdio.h>

int i, n;
long long res;

int main(void)
{
  scanf("%d",&n);
  res = 1;
  for(i = 1; i <= n; i++)
    res = res * i;
  printf("%lld\n",res);
  return 0;
}