module String = struct
  include String

  let fold_left f init str =
    let n = String.length str - 1 in
    let rec doit i acc =
      if i > n then acc
      else doit (i + 1) (f acc str.[i]) in
    doit 0 init

end

let () =
  let s = read_line () in
  let rec doit cnt (t, r, e) =
    if t < 1 || r < 1 || e < 2 then cnt
    else doit (cnt + 1) (t - 1, r - 1, e - 2) in
  String.fold_left (fun (t, r, e) c ->
    if c = 't' then t + 1, r, e
    else if c = 'r' then t, r + 1, e
    else if c = 'e' then t, r, e + 1
    else t, r, e)
    (0, 0, 0) s
  |> doit 0
  |> Printf.printf "%d\n"