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);
        int n = in.nextInt();
        int[] a = new int[n];
        int smallest=0;
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        int count=0;
        int max=0;
        int grt=0,sml=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<n;j++){
                if(i == j)
                    continue;
                if(a[i] + 1 == a[j])
                    grt++;
                if(a[i] - 1 == a[j])
                   sml++;
                if(a[i] == a[j])
                    count++;
            }
            if(sml>grt)
                count += sml;
            else 
                count += grt;
            if(count> max)
                max = count;
            count=sml=grt=0;
        }
        System.out.println(max+1);
        
       
    }
}