let read () = Scanf.scanf "%d %d " (fun x y -> x, y)

let () =
  let aw, ab = read () in
  let bw, bb = read () in
  let c, d = read () in
  if c <= ab then Printf.printf "%d\n" (aw + if d <= bw then d else bw)
  else
    let aw = aw - (c - ab) in
    let bw = bw + (c - ab) in
    Printf.printf "%d\n" (aw + if d <= bw then d else bw)