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();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = long.Parse(ReadLine());
        var a = NList;
        for (var i = 0; i < n; ++i)
        {
            if ((i + 1 < n && a[i] == a[i + 1]) || (i + 2 < n && a[i] == a[i + 2]))
            {
                WriteLine("Yes");
                return;
            }
        }
        WriteLine("No");
    }
}