using System;
using System.Collections.Generic;
using System.Text;
using sc = Scanner;
using System.Collections;
using System.Linq;


class Program
{
    static void Main(string[] args)
    {
        Solve();

#if DEBUG
        Console.WriteLine("終了するにはなにかキーを押して下さい...");
        Console.ReadKey();
#endif

    }

    static void Solve()
    {
        int n = sc.NextInt();
        int[] w = sc.NextIntArray();
        int sum = w.Sum();
        if (sum % 2 != 0)//奇数はダメ
        {
            Console.WriteLine("impossible");
        }
        HashSet<int>[] set = new HashSet<int>[2];
        set[0] = new HashSet<int>();
        set[1] = new HashSet<int>();
        set[0].Add(0);
        for (int i = 0; i < w.Length; i++)
        {
            foreach (var item in set[i % 2])
            {
                if (item + w[i] == sum/2)
                {
                    Console.WriteLine("possible");
                    return;
                }
                if (!set[(i+1)%2].Contains(item + w[i]))
                {
                    set[(i + 1) % 2].Add(item + w[i]);
                }
            }
        }
        Console.WriteLine("impossible");

#if DEBUG
        Console.WriteLine("local check"); // Visual Studioのローカル変数チェック用 MainにいくとSolve内のローカル変数消えちゃう
#endif 
    }

    static int f(int a, int b)
    {
        return a * b;
    }


 }



public static class Scanner
{
    public static string[] NextStrArray()
    {
        return Console.ReadLine().Split(' ');
    }

    public static long[] NextLongArray()
    {
        string[] s = NextStrArray();
        long[] a = new long[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = long.Parse(s[i]);
        }
        return a;
    }
    public static int[] NextIntArray()
    {

        string[] s = NextStrArray();
        int[] a = new int[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = int.Parse(s[i]);
        }
        return a;
    }
    public static int NextInt()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return int.Parse(tmp);
    }
    public static double NextDouble()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return double.Parse(tmp);
    }
    public static long NextLong()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return long.Parse(tmp);
    }
    public static double[] NextDoubleArray()
    {

        string[] s = NextStrArray();
        double[] a = new double[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = double.Parse(s[i]);
        }
        return a;
    }
}