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 n;
long long output=1;

int main(){
	scanf("%d",&n);
	for(int i=n;i>=1;i--){
		output*=i;
	}
	printf("%lld\n",output);
	return 0;
}