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 n = NN;
        var a = NList;
        var dic = new Dictionary<int, List<int>>();
        for (var i = 0; i < n; ++i)
        {
            if (dic.ContainsKey(a[i])) dic[a[i]].Add(i);
            else dic[a[i]] = new List<int>{ i };
        }
        var kmin = 1;
        var kmax = n - 1;
        foreach (var kv in dic)
        {
            if (kv.Value.Count > 2)
            {
                WriteLine("0");
                WriteLine();
                return;
            }
            else if (kv.Value.Count == 2)
            {
                kmin = Math.Max(kmin, kv.Value[0] + 1);
                kmax = Math.Min(kmax, kv.Value[1]);
            }
        }
        var ans = new List<int>();
        for (var i = kmin; i <= kmax; ++i) ans.Add(i);
        WriteLine(ans.Count);
        WriteLine(string.Join(" ", ans));
    }
}