import math

y=int(input())
x=int(input())
l=int(input())
direction=0
if x>0 and y!=0:
    direction=1
if x<0:
    direction=2
if x==0 and y!=0:
    direction=1
move=0
move+=math.ceil(abs(x)/l)
move+=math.ceil(abs(y)/l)
ans=direction+move
print(ans)