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];
        Hashtable<Integer, Integer> a = new Hashtable<>();
        for(int a_i=0; a_i < n; a_i++){
            int cur = in.nextInt();
            if(a.containsKey(cur))
                a.put(cur, a.remove(cur) + 1);
            else
                a.put(cur, 1);
        }
        Enumeration<Integer> keys = a.keys();
        int maxSoFar = 0;
        while(keys.hasMoreElements()){
            int cur = keys.nextElement();
            Integer less = a.get(cur - 1);
            Integer more = a.get(cur + 1);
            if(less == null)
                less = 0;
            if(more == null)
                more = 0;
            maxSoFar = Math.max(maxSoFar, Math.max(less, more) + a.get(cur));
        }
        System.out.println(maxSoFar);
    }
}