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 n;
		long sum = 1;
		
		n  =sc.nextInt();
		while (0 < n) {
			sum *= n;
			n--;
		}
		
		System.out.println(sum);
	}
}