import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
public class Solution 
{
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        int i,ans=0,count=Integer.MIN_VALUE;
        int n = sc.nextInt();
        int[] arr=new int[100];
        int[] a = new int[n];
        for(i=0; i < n; i++)
            a[i] = sc.nextInt();
        for(i=0;i<n;i++)
            arr[a[i]]+=1;
        for(i=1;i<99;i++)
        {
            if(arr[i]+arr[i+1]>count)
            {
                count=arr[i]+arr[i+1];
            }
        }
        if(arr[99]>count)
            count=arr[99];
        System.out.println(count);
    }
}