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.*;

public class Main {
    private static final Scanner scn = new Scanner(System.in);
    
    public static void main(String[] args) {
        System.out.println(factorial(scn.nextInt()));
    }
    
    private static long factorial(int n) {
        return n > 1 ? n * factorial(n - 1) : 1;
    }
}