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>

int main()
{
	int n;

	unsigned long long int s=1;

	std::cin >> n;

	for(int i=1;i<=n;++i)
	{
		s*=i;
	}

	std::cout << s << '\n';
}