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);
        
        a=a.OrderBy(i=>i).ToArray();
            int res = 0;            
            for (int i = 0; i < n; i++)
            {
                int res2 = 1;
                for (int j = i+1; j < n; j++)
                {                    
                    if (Math.Abs(a[i] - a[j]) <= 1)
                    {
                        res2++;
                    }
                    if (Math.Abs(a[i] - a[j]) > 1)
                        break;
                }
                res = res < res2 ? res2 : res;
            }
            Console.WriteLine(res);
        
    }
}