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 in = new Scanner(System.in);
        List<Integer> al=new ArrayList<Integer>();
        int n = in.nextInt();
        int count=0,countFL=Integer.MIN_VALUE;
        for(int a_i=0; a_i < n; a_i++){
            al.add(in.nextInt());
        }
        Collections.sort(al);
        for(int i=0;i<al.size()-1;i++)
        	{
        		count=0;
	        	for(int j=i+1;j<al.size();j++)
	        	{
	        		if(al.get(i)-al.get(j)==0 || al.get(i)-al.get(j)==1 || al.get(i)-al.get(j)==-1)
	        		{
	        			count++;
	        		}
	        		else 
	        			break;
	        	}
	        	
	        	if(count>countFL)
	        		countFL=count;
        	}
        System.out.println(countFL+1);
        		
    }
}