import strutils, sequtils, math

proc brr_y(k, x: float): auto = k - x
proc ufo(a, r: float): auto = a + r / (2.0).sqrt

let
  t = stdin.readLine.split.mapIt(float, it.parseFloat.abs)
  (x, y, r) = (t[0], t[1], t[2])
var
  k = 0

while ufo(y, r) >= brr_y(k.float, ufo(x, r)):
  k += 1

echo k