N,D=map(int,input().split())
print(int(N/((D*2)+1)) if N%((D*2)+1)==0 else int(N/((D*2)+1))+1)
cbe6e37f9556ad8168ffb6b8b2783f1ee733cdb5
<mask token>

<mask token>
print(int(N / (D * 2 + 1)) if N % (D * 2 + 1) == 0 else int(N / (D * 2 + 1)
    ) + 1)

N, D = map(int, input().split())
print(int(N / (D * 2 + 1)) if N % (D * 2 + 1) == 0 else int(N / (D * 2 + 1)
    ) + 1)

N,D=map(int,input().split())
print(int(N/((D*2)+1)) if N%((D*2)+1)==0 else int(N/((D*2)+1))+1)