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(void)
{
	int n,i;
	long long int sum;

	sum=1;

	scanf("%d",&n);

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

	printf("%lld\n",sum);

	return 0;
}