#!/usr/bin/env python

import math

x = abs(int(input().strip()))
y = int(input().strip())
l = int(input().strip())

if y < 0:
    ntimes = 2
    y = abs(y)
elif x == 0:
    ntimes = 0
else:
    ntimes = 1

ntimes += math.ceil(x/l)
ntimes += math.ceil(y/l)

print(int(ntimes))