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 long int x=1;

	cin >> n;
	for(int i=1; i<=n; i++) {
		x*=i;
	}
	cout << x << endl;

	return 0;

}