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[] argv) {
        long a=1L;
        for (int n=(new Scanner(System.in)).nextInt(); n>0; a*=n--);
        System.out.println(a);
    }
}