def movetime(x, y, max):
	cnt = 0
	if y < 0:
		cnt += 2
	elif x != 0:
		cnt += 1
	cnt += abs(y) / max + abs(x) / max
	if y % max != 0:
		cnt += 1
	if x % max != 0:
		cnt += 1
	return cnt

x = int(raw_input())
y = int(raw_input())
max = int(raw_input())

print movetime(x, y, max)