let length_accent s =
  let size = String.length s
  and i = ref 0 in
  let final_size = ref size in
    while !i < size do
      match s.[!i] with
	  'A'..'Z' | 'a'..'z' -> incr i
	| _ -> decr final_size; i := !i + 2
    done;
    !final_size
;;

let nth s pos =
  let i = ref 0
  and real_pos = ref 0
  and get pos =
    match s.[pos] with
	'A'..'Z' | 'a'..'z' -> s.[pos]
      | _ -> s.[pos + 1]
  in
    while (!i < pos) do
      match s.[!real_pos] with
	  'A'..'Z' | 'a'..'z' -> incr i; incr real_pos
	| _ -> incr i; real_pos := !real_pos + 2
    done;
    get !real_pos
;;