using System;
using System.Linq;

namespace No004_おもりと天秤
{
    class Program
    {
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            string[] input = Console.ReadLine().Split(' ');
            int[] weight = input.Select(int.Parse).ToArray();
            int total = weight.Sum();
            int sum = 0;

            if (total % 2 != 0)
            {
                Console.WriteLine("impossible");
                return;
            }

            Array.Sort(weight);

            for (int i = 1; sum < total / 2; i++)
            {
                int[] w2 = new int[i + 1];

                Array.Copy(weight, w2, i);
                sum = w2.Sum();

                if (sum == total / 2)
                {
                    Console.WriteLine("possible");
                    return;
                }
            }

            Console.WriteLine("impossible");
            return;
        }
    }
}