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