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;
long long f(int n){
	return (n == 0 ? 1 : n * f(n-1));
}
int main(){
	int n;
	cin >> n;
	cout << f(n) << endl;
}