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

namespace OmoriToTenbin
{
    class Program
    {

        public const int MaxOmoriWait = 100;

        static bool IsPossible(int HalfData, int Number, string[] Data, bool[] OmoriFlag)
        {

            for (int a = 0; a < Data.Length; a++)
            {
                OmoriFlag[int.Parse(Data[a])] = true;
            }

//            for (int c = 0; c < Data.Length; c++){
                for (int a = 0; a < Data.Length; a++)
                {
                    for (int b = OmoriFlag.Length - 1; b >= 0; b--)
                    {
                        if (OmoriFlag[b] == true)
                        {
                            if ((b + int.Parse(Data[a])) < (Number * MaxOmoriWait))
                            {
                               // if (b != int.Parse(Data[a]))
                               // {
                                    OmoriFlag[b + int.Parse(Data[a])] = true;
                                //}
                            }
                        }
                    }

  //              }
        }

            if (OmoriFlag[HalfData])
            {
                return true;
            }
            else
            {
                return false;
            }

        }

        static int CreateHalf(string[] Data)
        {
            int half = 0;
            
            for (int a = 0; a < Data.Length; a++)
            {
                half += int.Parse(Data[a]);
            }

            if ((half % 2) != 0)
            {
                return 0;
            }

            return half / 2;
        }

        static void Main(string[] args)
        {
            int Number;
            
            
            Number = int.Parse(Console.ReadLine()); //標準入力
            string[] Data = Console.ReadLine().Split(' ');//2つ以上のスペース区切り入力の取得
            

            /*
            Number = 7;
            string[] Data = { "20", "47", "73", "69", "26", "62", "89" };
            */

            bool[] OmoriFlag = new bool[Number * MaxOmoriWait];

            int HalfData = CreateHalf(Data);

            if (HalfData == 0)
            {
                Console.WriteLine("impossible\n");
                return;
            }

            if (IsPossible(HalfData, Number, Data, OmoriFlag))
            {
                Console.WriteLine("possible\n");
            }
            else
            {
                Console.WriteLine("impossible\n");
            }


        }
    }
}