let () =
  let s = read_line () in
  let n = String.length s in
  let rec doit i c w =
    if i = n then c, w
    else begin
      if s.[i] = 'c' then
        if c <> (-1) then doit (i + 1) c w
        else doit (i + 1) i w
      else if s.[i] = 'w' then
        if c = (-1) then doit (i + 1) c w
        else
          match w with
          | [] -> doit (i + 1) c (i :: w)
          | [_] -> c, i :: w
          | _ -> assert false
      else doit (i + 1) c w
    end in
  let (c, w) = doit 0 (-1) [] in
  let n =
    if c = (-1) then (-1)
    else
      match w with
      | [] | [_] -> (-1)
      | [w; _] -> if c >= w then (-1) else w - c + 1
      | _ -> assert false in
  Printf.printf "%d\n" n