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