import java.util.Scanner;

public class Main {

    public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    }
} Main public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    } main {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int d = sc.nextInt(); d sc.nextInt() sc.nextInt sc int range = d * 2 + 1; range d * 2 + 1 d * 2 d 2 1 int result = n % range == 0 ? n / range : n / range + 1; result n % range == 0 ? n / range : n / range + 1 n % range == 0 n % range n range 0 n / range n range n / range + 1 n / range n range 1 System.out.println(result) System.out.println System.out System System.out result String args[] args public class Main {

    public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    }
} public class Main {

    public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String args[]) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int range = d * 2 + 1;
        int result = n % range == 0 ? n / range : n / range + 1;

        System.out.println(result);
    }
}
