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 <stdio.h>

int main()
{
	int n;
	long x;

	x = 1;

	scanf("%d", &n);

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

	printf("%ld\n", x);

	return 0;
}