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);
		int num = Integer.parseInt(sc.next());
		System.out.println(calc(num));
		sc.close();
	}
	static long calc (int num) {
		if (num == 1) {
			return num;
		} else {
			return num * calc(num - 1);
		}
	}

}

