import java.io.*; import java.util.*; import java.util.stream.*; public class Main { static ArrayList> dp = new ArrayList<>(); static int[] values; public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int n = sc.nextInt(); values = new int[n]; for (int i = 0; i < n; i++) { values[i] = sc.nextInt(); dp.add(new HashSet<>()); } if (dfw(n - 1, 0)) { System.out.println("possible"); } else { System.out.println("impossible"); } } static boolean dfw(int idx, int v) { if (idx < 0) { return v == 0; } if (!dp.get(idx).contains(v)) { if (dfw(idx - 1, v + values[idx])) { return true; } if (dfw(idx - 1, Math.abs(v - values[idx]))) { return true; } dp.get(idx).add(v); } return false; } } class Utilities { static String arrayToLineString(Object[] arr) { return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n")); } static String arrayToLineString(int[] arr) { return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new)); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public int[] nextIntArray() throws Exception { return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); } public String next() throws Exception { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }