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() {
	unsigned long int x, ans=1;
	cin >> x;
	for (int i = 2; i <= x; i++) {
		ans *= i;
	}
	cout << ans<<endl;
}