let read () = Scanf.scanf "%d " (fun i -> i)

let solve w n m =
  let z = m / 2 in
  let s = Array.make (z + 1) false in
  s.(0) <- true;
  let t = Array.copy s in
  for i = 0 to n - 1 do
    for x = w.(i) to z do
      t.(x) <- s.(x) || s.(x - w.(i))
    done;
    Array.iteri (fun i e -> s.(i) <- e) t;
  done;
  t.(z)

let () =
  let n = read () in
  let w = Array.init n (fun _ -> read ()) in
  let m = Array.fold_left (+) 0 w in
  if m mod 2 = 1 then print_endline "impossible"
  else print_endline (if solve w n m then "possible" else "impossible")