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<cstdio>
typedef long long int ll;
ll f(ll n){return n==0?1:n*f(n-1);}
int main(){
  int n;scanf("%d",&n);printf("%lld\n",f(n));
}