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; cin >> n;
	long long fac = 1;
	while (--n) {
		fac *= (n+1);
	}
	cout << fac << endl;
}