using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string[] a_temp = Console.ReadLine().Split(' ');
        int[] a = Array.ConvertAll(a_temp,Int32.Parse);
        List<int[]> lists = new List<int[]>();
        foreach(var i in a)
        {
            lists.Add(a.Where(ai => ai == i || ai == i - 1).ToArray());
            lists.Add(a.Where(ai => ai == i || ai == i + 1).ToArray());
        }
        
        var v = lists.Select(l => l.Length).OrderByDescending(l => l).Where(l => l <= n).FirstOrDefault();
        Console.WriteLine(v);
    }
}