import math


x, y = (int(i) for i in input().split())
l = int(input())
count = 0

if y < 0:
    count += 1
if x != 0:
    count += 1
else:
    if y < 0:
        count += 1

x = abs(x)
y = abs(y)

count += int(math.ceil(float(x) / float(l)))
count += int(math.ceil(float(y) / float(l)))

print(count)