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 ans = n;
	while(--n >= 1){
		ans *= n;
	}
	cout << ans << endl;
}
