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 <cmath>
#include <iostream>
using namespace std;
int n;
int main() {
	cin >> n;
	cout << (long long)tgamma((long double)(n + 1)) << endl;
}