y = int(input())
x = int(input())
l = int(input())

res = 0

if x >= 0 and y == 0:
    res += 0
elif x >= 0:
    res += 1
else:
    res += 2

res += (abs(x) + l - 1) // l
res += (abs(y) + l - 1) // l

print(res)