import strutils, sequtils, math

proc brr_y(k: int, x: float): float =
  k.float - x

let
  t = stdin.readLine.split.map parseFloat
  (x0, y0, r) = (t[0].abs, t[1].abs, t[2])
  ufo_y = y0 + r / (2.0).sqrt
var
  k = 0

while ufo_y >= brr_y(k, x0 + r / (2.0).sqrt):
  k += 1

echo k