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

class Program
{
    static string InputPattern = "Input4";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("3");
            WillReturn.Add("1 2 3");
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("5");
            WillReturn.Add("1 2 3 4 5");
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("15");
            WillReturn.Add("62 8 90 2 24 62 38 64 76 60 30 76 80 74 72");
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();

        int[] OmoriArr =
            InputList.Skip(1).SelectMany(X => X.Split(' '), (X, Y) => int.Parse(Y)).ToArray();

        //事前に総和の半分を求めておく
        int OmoriSum = OmoriArr.Sum();

        //総和が奇数なら解なし
        if (OmoriSum % 2 == 1) {
            Console.WriteLine("impossible");
            return;
        }

        //作成可能な和を保持する配列
        bool[] CanCreateNum = new bool[OmoriSum / 2 + 1];
        CanCreateNum[0] = true;

        for (int I = 0; I <= OmoriArr.GetUpperBound(0); I++) {
            //同じ数を複数回使ってしますので、リバースループにする必要あり
            for (int J = CanCreateNum.GetUpperBound(0); 0 <= J; J--) {
                if (CanCreateNum[J] == false) continue;
                int wkInd = J + OmoriArr[I];
                if (wkInd <= CanCreateNum.GetUpperBound(0))
                    CanCreateNum[wkInd] = true;
            }
        }
        Console.WriteLine(CanCreateNum[OmoriSum / 2] ? "possible" : "impossible");
    }
}