import java.util.*;

public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    }
} import java.util.*; util.* java public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    }
} Main static Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) public static void main(String[]$) {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    } main {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    } int n = scanner.nextInt(); n scanner.nextInt() scanner.nextInt scanner int d = scanner.nextInt(); d scanner.nextInt() scanner.nextInt scanner System.out.println((n + d + d) / (d + d + 1)) System.out.println System.out System System.out (n + d + d) / (d + d + 1) (n + d + d) n + d + d n d d (d + d + 1) d + d + 1 d d 1 String[]$ $ public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    }
} public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    }
} Main
import java.util.*;

public class Main {
    static Scanner scanner = new Scanner(System.in);

    public static void main(String[]$) {
        int n = scanner.nextInt();
        int d = scanner.nextInt();
        System.out.println((n + d + d) / (d + d + 1));
    }
}