X=int(raw_input())
Y=int(raw_input())
L=int(raw_input())

Xabs=abs(X)
Yabs=abs(Y)

m=0
n=0

while Xabs>m*L:
    m+=1
while Yabs>n*L:
    n+=1

a=m+n
if Y<0:
    a+=2
if X!=0:
    a+=1
print(a)