let list_of_string str =
  let lstr = String.length str in
  let rec list_of_string' idx result =
    if idx >= lstr then result
    else list_of_string' (idx + 1) (str.[idx] :: result)
  in
  list_of_string' 0 []


let solve s =
  let c_lst = list_of_string s in
  let t_cnt = List.filter (fun c -> c = 't') c_lst |> List.length
  and r_cnt = List.filter (fun c -> c = 'r') c_lst |> List.length
  and e_cnt = List.filter (fun c -> c = 'e') c_lst |> List.length
  in
  min t_cnt (min r_cnt (e_cnt / 2))

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