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, i, ans = 1;
    cin >> n;
	for(i = 1; i <= n; i++){
		ans *= i;
	}
	cout << ans << endl;
	return 0;    
}