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 step(int s,long long a){
	if(s==0)return a;
	return step(s-1,a*s);
}

int main(){
	int n;
	scanf("%d",&n);
	printf("%lld\n",step(n,1));
	return 0;
}