Question 3

*/
import java.util.Scanner;
public class AssignmentQuestion3 {

    static int bunnyCounter=0;
    public static void main(String[] args){
         Scanner sc=new Scanner(System.in);
    int a=sc.nextInt();
    bunnyEars(a);
 System.out.print(bunnyCounter);
    }
    public static void bunnyEars(int x){


    if(x>0){
    bunnyCounter+=2;
    bunnyEars(x-1);

    }

    }


}