# coding: utf-8
import math

X = int(input())
Y = int(input())
L = int(input())

if X == 0 and Y == 0:
    print(0)
elif Y > 0:
    if X == 0:
        print(math.ceil(Y / L))
    else:
        print(math.ceil(Y / L) + 1 + math.ceil(abs(X) / L))
elif Y == 0:
    print(1 + math.ceil(abs(X) / L))
else:
    print(1 + math.ceil(abs(X) / L) + 1 + math.ceil(abs(Y) / L))