import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	}
} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	}
} Main public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	} main {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc int count = 1; count 1 int c = b + 1; c b + 1 b 1 while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        } a > (c + b) a (c + b) c b {
            count++;
            c = c + 2 * b + 1;
        } count++ count c = c + 2 * b + 1 c c + 2 * b + 1 c + 2 * b + 1 c 2 * b 2 b 1 System.out.print(count) System.out.print System.out System System.out count String[] args args public class Main {

	public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	}
} public class Main {

	public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	}
} Main
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        int b = sc.nextInt();
        int count = 1;
        int c = b + 1;
        while(a > (c + b)){
            count++;
            c = c + 2 * b + 1;
        }
        System.out.print(count);
	}
}