let () =
  let rec charlist_of_string str n i =
    if i = n then []
    else str.[i] :: charlist_of_string str n (i+1) in
  let rec count lst target =
    List.length (List.filter (fun x -> x = target) lst) in
  Scanf.scanf "%s\n" @@ fun s ->
  let lst = charlist_of_string s (String.length s) 0 in
  let t = count lst 't' in
  let r = count lst 'r' in
  let e = count lst 'e' in
  Printf.printf "%d\n"
    (if t < r && t * 2 <= e then t else if r <= t && r * 2 <= e then r else e / 2)