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;

long long n, r = 1;
int main() {
	cin >> n;
	for (long long i = 2; i <= n; ++i) r *= i;
	cout << r << '\n';
}
