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);
        
        var mc=0;
        for(var i=0;i<n;i++) {
            var c=1;
            for(var j=i+1;j<n;j++) {
                if((a[j]-a[i])>1)break;
                c++;
            }
            mc=Math.Max(c,mc);
        }
        
        Console.WriteLine(mc);
    }
}