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 int ans=1;
	for(int i=2; i<=n; i++){
		ans *= i;
	}
	cout << ans << endl;
	return 0;
}