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 ans = 1;
	do
	{
		ans *= n;
	} while (--n);
	cout << ans << endl;
	return 0;
}