import java.util.Scanner;
class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int ourNumber = scanner.nextInt();
        int squares=0;
       do {
           squares++;
       }while (squares<=ourNumber);
       if (squares%2!=1 && squares%2!=0)
       {System.out.println(squares);}

    }
}