let fl_help a hd =
  let (current, result) = a in
  match hd with
  | 'U' -> ('U', result)
  | 'M' when current = 'U' -> ('M', result)
  | 'G' when current = 'M' -> ('G', result + 1)
  | 'G' when current = 'G' -> ('G', result + 1)
  |  _ -> a;;


let calc s =
  let (_, result) = Seq.fold_left fl_help (' ', 0) s in
  result;;

let () =
  read_line () |> ignore;
  let seq = read_line () |> String.to_seq in
  calc seq |> print_int;
  print_newline ();;