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) {
		@SuppressWarnings("resource")
		Scanner sc = new Scanner(System.in);

		long inputNum = sc.nextInt();

		if (inputNum != 0) {
			for (int i = (int)inputNum; i > 1; i--) {
				inputNum *= (i - 1);
			}
			System.out.println(inputNum);
		} else {
			System.out.println(1);
		}
	}

}