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) {
		// TODO ?????????????????????????????????????????????
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		System.out.println(facto(n));
	}

	public static long facto(int n) {
		if (n == 1) return 1;

		return n * facto(n-1);
	}
}