using System;
using System.Linq;

namespace No004_おもりと天秤２
{
    class Program
    {
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            string[] input = Console.ReadLine().Split(' ');
            int[] list = input.Select(int.Parse).ToArray();
            int sum = list.Sum();
            bool[] dp = new bool[sum + list.Max() + 1];

            if (sum % 2 == 1)
            {
                Console.WriteLine("impossible");
                return;
            }
            dp[0] = true;

            for (int i = 0; i < list.Length; i++)
            {
                for (int j = 0; j <= sum; j++)
                {
                    if (dp[j] == true)
                    {
                        dp[j + list[i]] = true;
                    }
                }
            }

            if (dp[sum / 2] == true)
                Console.WriteLine("possible");
            else
                Console.WriteLine("impossible");
        }
    }
}