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>

using namespace std;

int main(){
	int n;
	cin>>n;
	long long r=1;
	for(int i=1; i<=n;i++){
		r=r*i;
	}
	cout<<r<<endl;
	
}	
