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

import math
count = 0
if y>=0:
    count = math.ceil(abs(y)/l)
else:
    count = math.ceil(abs(y)/l)+2

if x==0:
    print(count)
else:
    count+=math.ceil(abs(x)/l)
    count+=1
    print(count)