import math
x = int(input())
y = int(input())
l = int(input())

move = 0
if y < 0:
    move = 2
elif x !=0:
    move = 1

if x !=0:
    move += math.ceil(abs(x)/l)
if y !=0:
    move += math.ceil(abs(y)/l)

print(move)