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

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var a = NList;
        var ans = new List<int>();
        var count = new int[10];
        foreach (var ai in a) ++count[ai];
        for (var i = 1; i <= 9; ++i)
        {
            ++count[i];
            if (count.Count(ci => ci == 3) == 4 && count.Count(ci => ci == 2) == 1) ans.Add(i);
            --count[i];
        }
        WriteLine(ans.Count);
        WriteLine(string.Join(" ", ans));
    }
}