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

class Program
{
    static string InputPattern = "Input5";

    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 if (InputPattern == "Input4") {
            WillReturn.Add("100");
            WillReturn.AddRange(Enumerable.Repeat("100", 100));
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    struct JyoutaiDef
    {
        internal int CurrP;
        internal bool[] CanCreateSum;
    }

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

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

        //事前に総合計を求めておく
        int OmoriSum = OmoriArr.Sum();

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

        var stk = new Stack<JyoutaiDef>();
        JyoutaiDef WillPush;
        WillPush.CurrP = 0;
        WillPush.CanCreateSum = new bool[OmoriSum / 2 + 1];
        WillPush.CanCreateSum[0] = true;
        stk.Push(WillPush);

        bool FoundAnswer = false;
        while (stk.Count > 0) {
            JyoutaiDef Popped = stk.Pop();

            //クリア判定
            if (Popped.CanCreateSum[OmoriSum / 2]) {
                FoundAnswer = true;
                break;
            }

            if (Popped.CurrP >= OmoriArr.GetUpperBound(0))
                continue;

            WillPush.CurrP = Popped.CurrP + 1;
            WillPush.CanCreateSum = (bool[])Popped.CanCreateSum.Clone();

            for (int I = WillPush.CanCreateSum.GetUpperBound(0); 0 <= I; I--) {
                if (WillPush.CanCreateSum[I] == false)
                    continue;

                int wkInd = I + OmoriArr[WillPush.CurrP];
                if (wkInd <= WillPush.CanCreateSum.GetUpperBound(0)) {
                    WillPush.CanCreateSum[wkInd] = true;
                }
            }
            stk.Push(WillPush);
        }
        Console.WriteLine(FoundAnswer ? "possible" : "impossible");
    }
}