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

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var n = int.Parse(Console.ReadLine());
            var w = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
            var k = w.Sum();
            var c = new bool[n, k / 2 + 1];
            if (k % 2 != 0 || w.Any(x => x > k / 2))
            {
                Console.WriteLine("impossible");
            }
            else
            {
                c[0, 0] = true;
                c[0, w[0]] = true;
                for (var i = 1; i < n; i++)
                {
                    for (var j = 0; j <= k / 2; j++)
                    {
                        if (c[i - 1, j])
                        {
                            c[i, j] = true;
                            if (j + w[i] <= k / 2)
                            {
                                c[i, j + w[i]] = true;
                            }
                        }
                    }
                }
                if (c[n - 1, k / 2])
                {
                    Console.WriteLine("possible");
                }
                else
                {
                    Console.WriteLine("impossible");
                }
            }
        }
    }
}