X = int(input())
Y = int(input())
L = int(input())
if Y<0 and X!=0: n = 1
elif Y<0 and X==0: n = 2
else: n = 0
X = abs(X); Y = abs(Y)
if Y%L!=0 and Y!=0: n = n+Y//L+1
elif Y!=0: n = n+Y//L
if X%L!=0 and X!=0: n = n+X//L+2
elif X!=0: n = n+X//L+1
print(n)