import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  }
} import java.util.Scanner; Scanner java.util import java.util.ArrayList; ArrayList java.util import java.util.Collections; Collections 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() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  } main {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  } 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() * 2 + 1; B sc.nextInt() * 2 + 1 sc.nextInt() * 2 sc.nextInt() sc.nextInt sc 2 1 int cnt = 0; cnt 0 while (A > 0) {
      cnt++;
      A -= B;
    } A > 0 A 0 {
      cnt++;
      A -= B;
    } cnt++ cnt A -= B A B System.out.println(cnt) System.out.println System.out System System.out cnt 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() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  }
} public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  }
} Main
import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int A = sc.nextInt();
    int B = sc.nextInt() * 2 + 1;
    int cnt = 0;
    while (A > 0) {
      cnt++;
      A -= B;
    }
    System.out.println(cnt);
  }
}
