let solve s =
  let lstr = String.length s in

  let rec solve' idx result =
    if idx >= lstr then result
    else
      let t_cnt, r_cnt, e_cnt = result in
      let t_cnt, r_cnt, e_cnt =
        t_cnt + (if s.[idx] = 't' then 1 else 0),
        r_cnt + (if s.[idx] = 'r' then 1 else 0),
        e_cnt + (if s.[idx] = 'e' then 1 else 0)
      in
      solve' (idx + 1) (t_cnt, r_cnt, e_cnt)
  in
  let t_cnt, r_cnt, e_cnt = solve' 0 (0, 0, 0) in
  min t_cnt (min r_cnt (e_cnt / 2))

let () =
  let s = read_line () in
  solve s |> string_of_int |> print_endline