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<iostream>
using namespace std;

int main(){

long long int ans=1,n;

 cin >> n;

 for(int i=1;i<=n;i++) ans = ans * i;

 cout << ans << endl;
}