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() {
	long long n,s;
	cin >> n;
    s=1;
	for (n;n>0;n--) s*=n; 
	cout << s <<  endl;
	return 0;
	}