import java.io.*;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    }
} import java.io.*; io.* java import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    }
} Main public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    } main {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int N = scan.nextInt(); N scan.nextInt() scan.nextInt scan int D = scan.nextInt(); D scan.nextInt() scan.nextInt scan int count=0; count 0 count = (N+2*D)/(2*D+1) count (N+2*D)/(2*D+1) (N+2*D) N 2*D 2 D (2*D+1) 2*D 2 D 1 System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    }
} Main
import java.io.*;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int D = scan.nextInt(); 
        int count=0;
        count = (N+2*D)/(2*D+1);
        System.out.println(count);
    }
}