using System;

namespace OmoriToTenbin
{
    class Program
    {
        static int N;
        static int[] W;
        static int[] remainSum;

        static void Main(string[] args)
        {
            N = int.Parse(Console.ReadLine());
            W = new int[N];
            remainSum = new int[N];
            string[] vals = Console.ReadLine().Split(' ');

            for(int i=0; i < N; i++)
            {
                W[i] = int.Parse(vals[i]);
            }

            remainSum[N - 1] = W[N - 1];
            for (int i=N-2; i >= 0; i--)
            {
                remainSum[i] = remainSum[i + 1] + W[i];
            }

            if(Search(0, 0))
            {
                Console.WriteLine("possible");
            }
            else
            {
                Console.WriteLine("impossible");
            }

        }

        static bool Search(int weight, int n)
        {
            if (n == N - 1)
            {
                if (weight + W[n] == 0 || weight - W[n] == 0)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }

            if (Math.Abs(weight) > remainSum[n])
                return false;

            if(Search(weight+W[n], n+1))
            {
                return true;
            }
            if(Search(weight-W[n], n+1))
            {
                return true;
            }
            return false;
        }

    }
}