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

public class Program
{
	public static void Main()
	{
		int N = int.Parse(Console.ReadLine());
		int[] W = Console.ReadLine().Split().Select(int.Parse).ToArray();
		if (W.Sum() % 2 == 1)
		{
			Console.WriteLine("impossible");
			return;
		}
		int target = W.Sum() / 2;
		var flg = new bool[N + 1];
		flg[0] = true;
		var q = new Queue<int>();
		q.Enqueue(0);
		for (int i = 0; i < N; i++)
		{
			int len = q.Count;
			for (int j = 0; j < len; j++)
			{
				var t = q.Dequeue();
				q.Enqueue(t);
				q.Enqueue(t + W[i]);
			}
		}
		Console.WriteLine(q.Any(i => i == target) ? "possible" : "impossible");
	}
}