let () =
  let c = (ref 0, ref 1) in
  let w = ref 'c' in
  Scanf.scanf "%s\n" @@ fun s ->
  for i = 0 to String.length s - 1 do
    if !w <> 'w' && s.[i] = 'c' then (snd c := 1; w := 'W')
    else if !w = 'W' && s.[i] = 'w' then (snd c := !(snd c) + 1; w := 'w')
    else if !w = 'w' && s.[i] = 'w' 
    then (snd c := !(snd c) + 1; if !(snd c) < !(fst c) || !(fst c) = 0 
          then fst c := !(snd c); snd c := 1; w := 'c')
    else if !w = 'W' || !w = 'w' then (snd c := !(snd c) + 1)
  done;
  Printf.printf "%d\n" (if !(fst c) = 0 then -1 else !(fst c))