from sys import stdin

nii=lambda:list(map(int,stdin.readline().split()))

lnii=lambda:list(map(int,stdin.readline().split()))



n,d=nii()

print(((n+d*2+1-1)//(d*2+1)))
from sys import stdin

nii=lambda:list(map(int,stdin.readline().split()))

lnii=lambda:list(map(int,stdin.readline().split()))



n,d=nii()

num=d*2+1

print(((n+num-1)//num))
from sys import stdin

nii = lambda: list(map(int, stdin.readline().split()))
lnii = lambda: list(map(int, stdin.readline().split()))
n, d = nii()
print(((n + d * 2 + 1 - 1) // (d * 2 + 1)))

from sys import stdin

nii = lambda: list(map(int, stdin.readline().split()))
lnii = lambda: list(map(int, stdin.readline().split()))
n, d = nii()
num = d * 2 + 1
print(((n + num - 1) // num))

-print(((n + d * 2 + 1 - 1) // (d * 2 + 1))) +num = d * 2 + 1 +print(((n + num - 1) // num))