let () =
  let t = Array.make 13 0 in
  let s = read_line () in
  let rec doit i =
    if i = 13 then true
    else
      let x = Char.code s.[i] - Char.code 'a' in
      if x < 0 || x > 12 then false
      else begin
        t.(x) <- t.(x) + 1;
        doit (i + 1)
      end in
  if not (doit 0) then print_endline "Impossible"
  else
    let m = Array.fold_left max 0 t in
    if m > 2 then print_endline "Impossible"
    else if m = 2 then begin
      let rec doit i =
        if i = 13 then assert false
        else if t.(i) = 0 then i + Char.code 'a' |> Char.chr |> Printf.printf "%c\n"
        else doit (i + 1) in
      doit 0
    end else begin
      for i = 0 to 12 do
        i + Char.code 'a' |> Char.chr |> Printf.printf "%c\n"
      done
    end