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>

long long int fact(long long int n){
  return (n==0)? 1 : n*fact(n-1);
}

int main(){
  long long int n;
  scanf("%lld", &n);
  printf("%lld\n", fact(n));
}