# -*- coding:utf-8 -*-
import math
if __name__ == "__main__":
	x = input()
	y = input()
	l = input()
	ans = math.ceil(abs(x) / l) + math.ceil(abs(y) / l)
	if x != 0 and y != 0:
		ans += 1
	if x < 0:
		ans += 1
	print int(ans)