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
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextInt();
		System.out.println(fact(n));
	}
	static long fact(long n){
		if(n==0){
			return 1;
		}else{
			return n*fact(n-1);
		}
	}
}