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 long factorial(int n){
		if( n == 0 ){
			return 1;
		}
		return n*factorial(n-1);
	}
	
	public static void main(String[] args){
		Scanner stdIn = new Scanner(System.in);
		
		int n = stdIn.nextInt();
		System.out.println(factorial(n));
	}
}