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

count=0
turn=0

if Y>0:
    count+=int((Y+L-1)/L)

if X!=0:
    turn=1
    count+=int((abs(X)+L-1)/L)

if Y<0:
    turn=2
    count+=int((abs(Y)+L-1)/L)

count+=turn

print(count)