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

namespace yuki0004 {
    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 )
                .OrderByDescending( x => x ).ToList();
            const string POSSIBLE = "possible";
            const string IMPOSSIBLE = "impossible";
            if (w.Sum() % 2 == 1) return IMPOSSIBLE;
            var goal = w.Sum() / 2;
            var queue = new Queue<int>();
            queue.Enqueue( w[ 0 ] );
            queue.Enqueue( -1 );

            for (var i = 1; i != w.Count(); ++i) {
                while (true) {
                    var s = queue.Dequeue();
                    queue.Enqueue( s );
                    if (s == -1) break;
                    if (s == goal || s + w[ i ] == goal) return POSSIBLE;
                    else if (s + w[ i ] < goal && !queue.Contains( s + w[ i ] )) queue.Enqueue( s + w[ i ] );
                }
            }
            return IMPOSSIBLE;
        }

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