x = int(input())
y = int(input())
l = int(input())
num = 0

num += abs(y) // l + int(abs(y) % l != 0)
if x != 0:
    num += 1
num += abs(x) // l + int(abs(x) % l != 0)

if y < 0:
    num += 1

print(num)