import math

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

c = 0
if y > 0 and x == 0:
    c += math.ceil(y / l)

elif y > 0 and x != 0:
    c += math.ceil(y / l)
    c += 1 + abs(math.ceil(x / l))

elif y < 0 and x == 0:
    c += 2 + math.ceil(y / l)

elif y < 0 and x != 0:
    c += 1 + abs(math.ceil(x / l))
    c += 1 - math.ceil(y / l)

elif y == 0 and x != 0:
    c += 1 + abs(math.ceil(x / l))

print(c)