import math

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

tmp=0

meirei=0
if Y>=0 and X==0:
    meirei=math.ceil(Y/L)
    print(meirei)
elif Y>=0 and X!=0:
    tmp=abs(X/L)
    meirei=1+math.ceil(Y/L)+math.ceil(tmp)
    print(meirei)
else:
    meirei=2
    tmp=abs(X/L)
    meirei+=math.ceil(tmp)
    tmp=0
    tmp=abs(Y/L)
    meirei+=math.ceil(tmp)
    print(meirei)