let () = Scanf.scanf "%d" @@ fun n ->
  let pow = Array.make 12 0 in
  pow.(0) <- 1;
  for i = 0 to 10 do
    pow.(i + 1) <- 26 * pow.(i)
  done;
  let rec aux n d (p :: ps) k =
    if n < p
    then k n d
    else aux (n - p) (d + 1) ps k in
  let rec solve acc n = function
    | 0 -> acc
    | d -> solve (Char.chr (Char.code 'a' + n mod 26) :: acc) (n / 26) (d - 1) in
  List.iter print_char @@ aux n 0 (Array.to_list pow) @@ solve ['\n']

