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 fact(int n){
	if(n==0) return 1;
	else return n*fact(n-1);
}

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