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 {

    public static void main(String[] args) {
	    Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        long b =1;
        for (int i =1;i<=a;i++){
            b=b*i;
        }
        System.out.println(b);
    }
}