open Batteries
let n = read_int ()

let a = int_of_char 'a'


let get_char i = if i = 0 then 'z' else char_of_int @@ a - 1 + i

let rec loop now result_lst =
  if now <= 26 then (get_char now) :: result_lst else
  loop (now / 26) (get_char (now mod 26) :: result_lst)
(* charのlistをstringに *)
let string_of_chars chars = 
  let buf = Buffer.create 16 in
  List.iter (Buffer.add_char buf) chars;
  Buffer.contents buf
let _ = print_endline @@ string_of_chars @@ loop n []