import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

from math import ceil

x = int(readline())
y = int(readline())
l = int(readline())
if y < 0:
    y = abs(y) + 7
if x != 0:
    x = abs(x) + 7
print(ceil(y / l) + ceil(x / l))