import java.util.Scanner;

public class Main{

    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    }
} import java.util.Scanner; Scanner java.util public class Main{

    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    }
} Main public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    } main {
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int woods = scan.nextInt(); woods scan.nextInt() scan.nextInt scan int peoples = scan.nextInt(); peoples scan.nextInt() scan.nextInt scan System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0))) System.out.println System.out System System.out (int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)) Math.ceil Math (double)woods / (peoples * 2.0 + 1.0) (double)woods (peoples * 2.0 + 1.0) peoples * 2.0 peoples 2.0 1.0 String[] args args public class Main{

    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    }
} public class Main{

    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    }
} Main
import java.util.Scanner;

public class Main{

    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);

        // input
        int woods = scan.nextInt();
        int peoples = scan.nextInt();

        // answer
        System.out.println((int)Math.ceil((double)woods / (peoples * 2.0 + 1.0)));

    }
}