#!/usr/bin/python
# -*- coding: utf-8 -*-
import math
X = int(raw_input())
Y = int(raw_input())
L = int(raw_input())
ans = 0

if X != 0:
       	ans += 1 + math.ceil(math.fabs(X) * 1.0 / L)
elif X == 0 and Y < 0:
       	ans += 2 + math.ceil(math.fabs(Y) * 1.0 / L)
       	print int(ans)
       	exit()

if Y > 0:
       	ans += math.ceil(math.fabs(Y) * 1.0 / L)
print int(ans)