using System;
using System.Collections.Generic;
using System.Linq;

namespace yuki0004 {
    public struct Node {
        public int s0, s1;
    }
    public class Program {
        static internal string Solve(System.IO.TextReader reader) {
            var n = int.Parse( reader.ReadLine() );
            var w = reader.ReadLine().Split().ToList().ConvertAll( int.Parse );
            var aim = w.Sum() / 2;
            if (w.Sum() % 2 == 1 || w.Max() > aim) return "impossible";
            if (w.Contains( aim )) return "possible";
            var q = new Queue<Node>();
            Node node = new Node { s0 = 0, s1 = w[ 0 ] };
            q.Enqueue( node );
            for (var i = 1; i <= n; ++i) {
                var r = new List<Node>();
                while (q.Any()) {
                    var t0 = q.Dequeue();
                    Node t1 = new Node { s0 = t0.s0 + w[ i ], s1 = t0.s1 };
                    Node t2 = new Node { s0 = t0.s0, s1 = t0.s1 + w[ i ] };
                    if (t1.s0 == aim) return "possible";
                    else if (t1.s0 < aim) r.Add( t1 );
                    if (t2.s1 == aim) return "possible";
                    else if (t2.s1 < aim) r.Add( t2 );
                }
                foreach (var e in r) q.Enqueue( e );
            }
            return "impossible";
        }

        static void Main(string[] args) {
            Console.WriteLine( Solve( System.Console.In ) );
        }
    }
}