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

namespace YukiCoder
{
    class Program
    {
        static int nMax;
        static Int32[] pv;
        static Int32 pvSum;
        static bool zzz(int ni, int vi)
        {
            if ((vi * 2) == pvSum) return true;
            if (ni >= nMax) return false;

            if (zzz(ni + 1, vi)) return true;
            return zzz(ni + 1, vi + pv[ni]);
        }

        
        static void Main(string[] args)
        {
            nMax = int.Parse(Console.ReadLine());
            pv = Console.ReadLine().Split().Select(int.Parse).ToArray();
            //pv = new Int32[nMax + 1];
            pvSum = pv.Sum();
            if (zzz(0, 0))  Console.WriteLine("possible");
            else            Console.WriteLine("impossible");
            Console.ReadLine();
        }
    }
}