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(){

	long int a, r=0;

	scanf("%ld",&a);

	r = a;

	for(int i=a-1; i>0; i--){
		r = r * i;
	}

	printf("%ld\n", r);
}