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 in = sc.nextInt();
		long result = 1L;
		
		for (int i = in; i >=1; i--){
			result *= i;
		}
		System.out.println(result);
		
		sc.close();
	}
}