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);
        Array.Sort(a);
        int result = 0;
        for (int x = n - 1; x >= 0; x--)
        {
            int temp = 1;
            for (int y = 0; y < x; y++)
            {
                if (a[x] - a[y] <= 1)
                    temp++;
            }
            result = Math.Max(result, temp);
        }
        Console.WriteLine(result);
    }
}