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 int n, a = 1;

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