from math import ceil
X = int(input())
Y = int(input())
L = int(input())

count = 0

if Y >= 0 and X == 0:
    count = ceil(Y / L)
elif Y >= 0 and abs(X) > 0:
    count = ceil(Y / L) + 1 + ceil(abs(X) / L)
else:
    count = ceil(abs(X) / L) + ceil(abs(Y) / L) + 2

print(count)