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,a=1;
	cin >> n;
	for (int i = (int)n; i >= 2; i--){
		a *= i;
	}
	cout << a << endl;
}