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();
        ArrayList<Integer> list = new ArrayList<Integer>();
        HashMap<Integer,Integer> count = new HashMap<Integer,Integer>();
        for(int a_i=0; a_i < n; a_i++){
            int x = in.nextInt();
            list.add(x);
            if(count.containsKey(x)) {
                count.put(x,count.get(x)+1);
            } else {
                count.put(x,1);
            }
        }
        Collections.sort(list);
        int ans = 0;
        while(list.size()>0) {
            int y = list.get(0);
            int z = 0;
            if(count.containsKey(y+1)) {
                z = count.get(y) + count.get(y+1);
            } else {
                z = count.get(y);
            }
            if(z>ans) {
                ans = z;
            }
            while(list.size()>0 && list.get(0)==y) {
                list.remove(0);
            }
        }
        System.out.println(ans);
    }
}