open Printf
open Scanf

let () =
  let mx = 10001 in
  let n = scanf "%d " (fun x -> x) in
  let ws = Array.init n (fun _ -> let w = scanf "%d " (fun x -> x) in w) in
  let dp = Array.make_matrix (n+1) mx false in
  let rec loop i j =
    if i = n then ()
    else if j = mx then loop (i+1) 0
    else if dp.(i).(j) then begin
        dp.(i+1).(j+ws.(i)) <- true;
        dp.(i+1).(abs (j - ws.(i))) <- true;
        loop i (j+1)
      end
    else loop i (j+1) in
  dp.(0).(0) <- true;
  loop 0 0;
  printf "%s\n" (if dp.(n).(0) then "possible" else "impossible")