using System;
using System.Linq;

namespace No004_おもりと天秤
{
    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();
            int[,] a = new int[3, 6];
            bool[,] dp = new bool[101, 10001];

            if (sum % 2 == 1)
            {
                Console.WriteLine("impossible");
                return;
            }

            dp[0, 0] = true;

            for (int i = 0; i < list.Length; i++)
            {
                for (int j = 0; j <= 20; j++)
                {
                    if (dp[i, j] == true)
                    {
                        dp[i + 1, j + list[i]] = true;
                        dp[i + 1, j] = true;
                    }
                }
            }

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