using System;
using System.Linq;

namespace No004_おもりと天秤
{
    class Program
    {
        static private int N;
        static private int[] W;
        static private int AllSum;

        static void Main(string[] args)
        {
            N = int.Parse(Console.ReadLine());
            string[] input = Console.ReadLine().Split(' ');
            W = input.Select(int.Parse).ToArray();

            AllSum = 0;
            foreach (int a in W)
                AllSum += a;

            for (int i = 0; i < N; i++)
                Count(i, 0);

            Count(0, 0);

            if (AllSum == -1)
                Console.WriteLine("possible");
            else
                Console.WriteLine("impossible");
        }

        static void Count(int level, int sum)
        {
            sum += W[level];

            if (AllSum - sum == sum)
            {
                AllSum = -1;
            }
            else if (AllSum != -1 && level < N - 1)
            {
                Count(level + 1, sum);
            }
        }
    }
}