X = int(input())
Y = int(input())
L = int(input())
i = 0

if Y < 0:
	i += 2
if X != 0:
	i += 1
if (X<0 and Y>=0) or (X>=0 and Y<0):
	i += (X//L + Y//L)* -1
else:
	i += X//L + Y//L
if X%L != 0:
	i+= 1
if Y%L != 0:
	i+= 1
print(i)