import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    }
} Main public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    } main {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    } Scanner in = new Scanner(System.in); in new Scanner(System.in) int num = in.nextInt(); num in.nextInt() in.nextInt in int dis = in.nextInt(); dis in.nextInt() in.nextInt in in.close() in.close in dis += dis + 1 dis dis + 1 dis 1 int ans = num / dis; ans num / dis num dis if (num % dis != 0) {
            ans++;
        } num % dis != 0 num % dis num dis 0 {
            ans++;
        } ans++ ans System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        int dis = in.nextInt();
        in.close();
        dis += dis + 1;
        int ans = num / dis;
        if (num % dis != 0) {
            ans++;
        }
        System.out.println(ans);
    }
}