using System;
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();
            if (w.Sum() % 2 == 1) return "impossible";
            var aim = w.Sum() / 2;
            int subtotal=0;
            for(var i = 0; i != n; ++i) {
                if (subtotal + w[ i ] == aim) return "possible";
                else if (subtotal + w[ i ] < aim) subtotal += w[ i ];
                else continue;
            }
            return "impossible";
        }

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