import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    }
} Main public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    } main {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int d = sc.nextInt(); d sc.nextInt() sc.nextInt sc int coverage = d * 2 + 1; coverage d * 2 + 1 d * 2 d 2 1 int ans = 0; ans 0 for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        } int i = 1; int i = 1; i 1 i <= n i n i++ i++ i {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        } {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        } for (int j = 1; j < coverage; j++) {
                i++;
            } int j = 1; int j = 1; j 1 j < coverage j coverage j++ j++ j {
                i++;
            } {
                i++;
            } i++ i 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 sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    }
} public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    }
} Main
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();

        int coverage = d * 2 + 1;
        int ans = 0;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j < coverage; j++) {
                i++;
            }
            ans++;
        }
        System.out.println(ans);
    }
}
