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);
        int[] num = new int[100];
        for(int i=0; i<n; i++) {
            num[a[i]]++;
        }
        int maxSum = 0;
        for(int j=0; j<(100-1); j++) {
            int sum = num[j]+num[j+1];
            if (sum > maxSum) {
                maxSum = sum;
            }
        }
        Console.WriteLine(maxSum);
    }
}