let n = Scanf.sscanf (read_line ()) "%d" @@ fun n -> n

let code_a = int_of_char 'a'

let char_of_code code = char_of_int (code_a + code)

let rec alp_of_int acc n =
  let acc = (n mod 26) :: acc in
  if n > 25 then alp_of_int acc (n / 26 - 1)
  else acc

let () = 
  (n - 1) |> alp_of_int [] |> List.map char_of_code |> List.map Char.escaped |> String.concat "" |> print_endline