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(){
	int n, i;
	long ans = 1;
	cin >> n;
	for(i=1;i<=n;i++){
		ans *= i;
	}
	cout << ans << endl;
	return 0;
}