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 <bits/stdc++.h>
#define r(i,n) for(int i;i<n;i++)
using namespace std;
int main(){
long long a,s=1;
cin>>a;
r(i,a+1)if(i)s*=i;
cout<<s<<endl;
}