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 {

	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		System.out.println( factional( sc.nextInt() ) );
	}

	private static long factional(int nextInt) {
		int n = nextInt;

		long ans = (n == 0) ? 1: n * factional(n - 1);

		return ans;
	}

}
