using System;
using System.Linq;

namespace OmoriTenbin
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            int[] P = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
            string R = MainProcess(N, P);
            Console.WriteLine(R);
        }

        private static string MainProcess(int N, int[] P)
        {
            const string imp = "impossible";
            const string pos = "possible";
            int sum = 0;
            foreach(int p in P) sum += p;
            if (sum % 2 != 0) return imp;
            int hlf = sum / 2;
            int max = P.Max();
            if (max > hlf) return imp;
            if (max == hlf) return pos;
            bool[] W = new bool[sum + 1];
            for (int i = 0;i < N ; i++)
            {
                for (int j = sum - 1 - P[i]; j > 0; j--)
                {
                    W[j+ P[i]] |= W[j];
                    if (W[j + P[i]] && j + P[i] == hlf)
                        return pos;
                }
                W[P[i]] = true;
            }
            return imp;
        }
    }
}