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

namespace No4_4{
    public class Program{
        public static void Main(string[] args){
            Console.ReadLine();
            var ws = Console.ReadLine().Split().ToList().ConvertAll(int.Parse);
            var dp = new List<int>{0};

            dp = ws.Aggregate(dp, (l, w) => l.Union(l.Select(i => i + w)).ToList());
            Console.WriteLine(ws.Sum() % 2 == 0 && dp.Contains(ws.Sum() / 2) ? "possible" : "impossible");
        }
    }
}