let () =
  let soc = fun n -> Char.escaped (char_of_int (97+n)) in
  let rec check n m l = if n <= m then (n-1, l-1) 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 -> Printf.printf "%s\n" (make (check n 26 1))