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 a = 1;
		long n = sc.nextInt();
		for(int i = (int)n ; i >= 1 ; i--){
			a = i * a;

		}
		System.out.println(a);
		sc.close();
	}

}