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

namespace Application
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			var N = readInt ();
			var A = readInts (' ');

			var s = new Searcher ();
			var l = 0;

			while (l < N) {
				l = s.LonguestSeq (A, l);
			}

			writeLine (s.Longest);
		}

		public class Searcher
		{
			public int Longest = 0;
			private Queue<int> distinct = new Queue<int> ();

			public int LonguestSeq (int[] A, int l)
			{
				var i = l + distinct.Count;
				for (; i < A.Length && !distinct.Contains (A [i]); i++) {
					distinct.Enqueue (A [i]);
				}

				this.Longest = Math.Max (distinct.Count, this.Longest);
				while (true) {
					l++;

					if (distinct.Count == 0)
						break;

					if (A.Length <= i)
						break;

					if (A [i] == distinct.Dequeue ())
						break;
				}

				var rest = A.Length - l;

				if (this.Longest > (rest + distinct.Count))
					l = A.Length;

				return l;
			}
		}

		static void writeLine (object o)
		{
			System.Console.WriteLine (o.ToString ());
		}

		static string readItem ()
		{
			return readItems (' ') [0];
		}

		static String[] readItems (char c)
		{
			return System.Console.ReadLine ().Split (c);
		}

		static int readInt ()
		{
			return readInts (' ') [0];
		}

		static int[] readInts (char c)
		{
			return readItems (c).Select (x => int.Parse (x)).ToArray ();
		}
	}
}