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

class Program
{
    static string InputPattern = "Input4";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("5");
            WillReturn.Add("1 2 3 1 2");
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("5");
            WillReturn.Add("1 2 3 4 5");
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("5");
            WillReturn.Add("1 1 1 1 1");
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();
        int[] AArr = InputList[1].Split(' ').Select(X => int.Parse(X)).ToArray();

        int UB = AArr.GetUpperBound(0);

        int Answer = 0;
        var wkList = new List<int>();

        foreach (int EachVal in AArr) {
            //再登場の数値の場合は、左からその数値までRemove
            if (wkList.Contains(EachVal)) {
                while (true) {
                    int DeleteVal = wkList[0];
                    wkList.RemoveAt(0);
                    if (DeleteVal == EachVal)
                        break;
                }
            }
            wkList.Add(EachVal);

            if (Answer < wkList.Count)
                Answer = wkList.Count;
        }
        Console.WriteLine(Answer);
    }
}