using System;
using System.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Math;

class Program
{
    static void Main()
    {
        var n = int.Parse(ReadLine());
        var w = ReadLine().Split().Select(int.Parse).ToArray();
        var s = w.Sum();
        if (s % 2 == 1)
        {
            WriteLine("impossible");
            return;
        }

        var dp = new bool[n, s + 1];
        dp[0, w[0]] = true;
        for (int i = 1; i < n; i++)
        {
            for (int j = 0; j < s + 1; j++)
            {
                if (j >= w[i]) dp[i, j] |= dp[i - 1, j - w[i]];
                dp[i, j] |= dp[i - 1, j];
            }
        }
        WriteLine(dp[n - 1, s] ? "impossible" : "possible");
    }
}