let () =
  let w,a,b = Scanf.scanf "%d %d %d " (fun a b c -> a,b,c) in

  let t = if a < b then
      b-a-w
    else if a > b then
      a-b-w
    else 0
  in
  Printf.printf "%d\n" @@
    if t <= 0 then 0 else t
