import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    }
} import java.util.Scanner; Scanner java.util public class Main{
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    }
} Main public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    } main {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int tree = sc.nextInt(); tree sc.nextInt() sc.nextInt sc int look = sc.nextInt(); look sc.nextInt() sc.nextInt sc int people = 0; people 0 while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        } tree >= look * 2 + 1 tree look * 2 + 1 look * 2 look 2 1 {
            people++;
            tree -= look * 2 + 1;
        } people++ people tree -= look * 2 + 1 tree look * 2 + 1 look * 2 look 2 1 if (tree > 0) {
            people++;
        } tree > 0 tree 0 {
            people++;
        } people++ people System.out.println(people) System.out.println System.out System System.out people String[] args args public class Main{
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    }
} public class Main{
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    }
} Main
import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
        // TODO code application logic here
        Scanner sc = new Scanner(System.in);
        int tree = sc.nextInt();
        int look = sc.nextInt();
        int people = 0;
        while (tree >= look * 2 + 1) {
            people++;
            tree -= look * 2 + 1;
        }
        if (tree > 0) {
            people++;
        }
        System.out.println(people);
    }
}
