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;
	long long int a = 1;
	cin >> n;
	for(int i = n; i > 0; i--){
		a *= i;
	}

	cout << a << endl;

	return 0;
}