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 n = sc.nextInt();
		int arr[]=new int[100];
		
		for(int i=0;i<n;i++)
		{
			int t = sc.nextInt();
			arr[t]++;
		}
		//int ar[] = new int[98];
		int an=0,an1=0;
		
		for(int j=1;j<99;j++)
		{
			an=arr[j] + arr[j+1];
			if(an > an1)
			an1=an;
		}
		System.out.println(an1);
    }
}