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 obj = new Scanner(System.in);
	        int n = obj.nextInt();
	        int[] a = new int[n];
	        int[] b = new int[n];
	        int i,j,count=0,ter=0;
	        for(i=0; i < n; i++){
	            a[i] = obj.nextInt();
	        }
	        
	        for(i=0;i<n;i++){
	        	count=0;
	        	for(j=0;j<n;j++){
	        	  
	        		if((a[j]==a[i])||(a[j]==a[i]+1)){
	        			count++;
	        		}
	        		b[i]=count;
	        		
	        		
	        	}
	        	
	        }
	        
	        Arrays.sort(b);
	        System.out.println(b[n-1]);
	    }
}