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;

	cin >> n;

	for (long long i = n - 1; i > 0; i--)
		n *= i;

	cout << n << endl;

	return 0;
}
