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)
{
	long long int s;
	int n,i;
	scanf("%d",&n);
	s=1;
	for(i=2;i<=n;i++){
		s=s*i;
	}
	printf("%lld\n",s);
	return 0;
}