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;
	long res = 1;
	cin >> n;
	for (int i = 2; i <= n; i++) {
		res *= i;
	}
	cout << res << endl;
	return 0;
}