let () =
  let soc = fun n -> Char.escaped (char_of_int (97+n)) in (* 0 -> a 25 -> z *)
  let rec check n m l = if n <= m then (n, l) else check (n-m) (m*26) (l+1) in
  let rec make n k =
    if k = 0 && n = 0 then soc n
    else if k = 0 then soc n
    else
      let y = int_of_float (26. ** (float_of_int k)) in
      let x, m = n / y, n mod y in soc x ^ make m (k-1) in
  Scanf.scanf "%d\n" @@ fun n ->
  let (n,k) = (check n 26 1) in
  Printf.printf "%s\n" (make (n-1) (k-1))