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

namespace No4_3{
    public class Program{
        public static void Main(string[] args){
            Console.ReadLine();
            var ws = Console.ReadLine().Split().ToList().ConvertAll(int.Parse);
            var dp = new HashSet<int>{0};

            foreach(var w in ws)
                dp.UnionWith(dp.Select(i => i + w).ToList());

            Console.WriteLine(
                ws.Sum() % 2 == 0 && dp.Contains(ws.Sum() / 2)
                    ? "possible"
                    : "impossible"
            );
        }
    }
}