using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace template
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] x = Console.ReadLine().Split().Select(int.Parse).ToArray();
            bool[,] dp = new bool[n, 100000];
            dp[0, 50000 + x[0]] = true; dp[0, 50000 - x[0]] = true;
            for (int i = 1; i < n; i++)
            {
                for (int j = 0; j < 100000; j++)
                {
                    if (dp[i - 1, j])
                    {
                        dp[i, j + x[i]] = true;
                        dp[i, j - x[i]] = true;
                    }
                }
            }
            Console.WriteLine(dp[n - 1, 50000] ? "possible" : "impossible");
        }
    }
}