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 <cstdio>

long rec(int n){
	if(n==1){
		return n;
	}
	else{
		return n * rec(n-1);
	}
}

int main(){
 	int n;
	scanf("%d",&n);
	printf("%ld\n",rec(n));
	return 0;
}