n, d = list(map(int, input().split()))

cover = 2 * d + 1

answer = n // cover

if n % cover:

    answer += 1

print(answer)
import sys



sr = lambda: sys.stdin.readline().rstrip()

ir = lambda: int(sr())

lr = lambda: list(map(int, sr().split()))



N, D = lr()

# 2 * D + 1

answer = (N + 2 * D) // (2 * D + 1)

print(answer)

n, d = list(map(int, input().split()))
cover = 2 * d + 1
answer = n // cover
if n % cover:
    answer += 1
print(answer)

import sys

sr = lambda: sys.stdin.readline().rstrip()
ir = lambda: int(sr())
lr = lambda: list(map(int, sr().split()))
N, D = lr()
# 2 * D + 1
answer = (N + 2 * D) // (2 * D + 1)
print(answer)

-n, d = list(map(int, input().split())) -cover = 2 * d + 1 -answer = n // cover -if n % cover: -    answer += 1 +import sys + +sr = lambda: sys.stdin.readline().rstrip() +ir = lambda: int(sr()) +lr = lambda: list(map(int, sr().split())) +N, D = lr() +# 2 * D + 1 +answer = (N + 2 * D) // (2 * D + 1)