Problem: There are N apple trees in a row. People say that one of them will bear golden apples.  We want to deploy some number of inspectors so that each of these trees will be inspected.  Each inspector will be deployed under one of the trees. For convenience, we will assign numbers from 1 through N to the trees. An inspector deployed under the i-th tree (1 \leq i \leq N) will inspect the trees with numbers between i-D and i+D (inclusive).  Find the minimum number of inspectors that we need to deploy to achieve the objective.

Submission attempts (in order):
from math import factorial as fact
import math
import sys
import itertools
import numpy as np
from collections import Counter
import datetime
from collections import deque



def input1():
	return int(input())


def input2():
	return map(int,input().split())


def input_array():
	return list(map(int,input().split()))

def keta(N):
	return len(str(N))


def input_daytime(input_time):
	time,distance=input_time.split()
	t=time.split(":")
	se=str(t[-1]).split(".")
	dt1 = datetime.timedelta(hours=int(t[0]),minutes=int(t[1]),seconds=int(se[0]),milliseconds=int(se[1]))
	return dt1

def combinations(n,r):
	return list(itertools.combinations(range(n),r))



def all_sets(num_list):
	subsets=[]
	for i in range(2,len(num_list) + 1):
		for c in combinations(num_list, i):
			subsets.append(c) 
	return subsets


def ch(x1):
	cf=[]
	for i in range(2,math.sqrt(x1)+1):
		if x1 % i==0:
			cf.append(i)
	return cf

def CountOneRoots(x,y):
	
	return fact(x+y)/fact(x)/fact(y)


def prime_factorize(n):
    a = []
    while n % 2 == 0:
        a.append(2)
        n //= 2
    f = 3
    while f * f <= n:
        if n % f == 0:
            a.append(f)
            n //= f
        else:
            f += 2
    if n != 1:
        a.append(n)
    return a
	
def count_str(m):
	tmp={}
	for i in range(10):
		if i in tmp:
			tmp[i]=1
		else:
			tmp[i]+=1
	return tmp

def is_prime(n):
	if n==1: return True

	for i in range(2,int(math.sqrt(n))+1):
		if n%i==0:
			return False
	return True


n,d=input2()

print(math.ceil(n//(d*2+1)))





from math import factorial as fact
import math
import sys
import itertools
import numpy as np
from collections import Counter
import datetime
from collections import deque



def input1():
	return int(input())


def input2():
	return map(int,input().split())


def input_array():
	return list(map(int,input().split()))

def keta(N):
	return len(str(N))


def input_daytime(input_time):
	time,distance=input_time.split()
	t=time.split(":")
	se=str(t[-1]).split(".")
	dt1 = datetime.timedelta(hours=int(t[0]),minutes=int(t[1]),seconds=int(se[0]),milliseconds=int(se[1]))
	return dt1

def combinations(n,r):
	return list(itertools.combinations(range(n),r))



def all_sets(num_list):
	subsets=[]
	for i in range(2,len(num_list) + 1):
		for c in combinations(num_list, i):
			subsets.append(c) 
	return subsets


def ch(x1):
	cf=[]
	for i in range(2,math.sqrt(x1)+1):
		if x1 % i==0:
			cf.append(i)
	return cf

def CountOneRoots(x,y):
	
	return fact(x+y)/fact(x)/fact(y)


def prime_factorize(n):
    a = []
    while n % 2 == 0:
        a.append(2)
        n //= 2
    f = 3
    while f * f <= n:
        if n % f == 0:
            a.append(f)
            n //= f
        else:
            f += 2
    if n != 1:
        a.append(n)
    return a
	
def count_str(m):
	tmp={}
	for i in range(10):
		if i in tmp:
			tmp[i]=1
		else:
			tmp[i]+=1
	return tmp

def is_prime(n):
	if n==1: return True

	for i in range(2,int(math.sqrt(n))+1):
		if n%i==0:
			return False
	return True


n,d=input2()

print(math.ceil(n/(d*2+1)))





Verdicts: Wrong Answer

Accepted