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];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        
        System.out.println(pickingNumbers(a));
    }
    
    public static int pickingNumbers(int[] arr){
        HashMap<Integer, Integer> setCounts = new HashMap<Integer, Integer>();
        for(int i = 0; i < arr.length; i++){
            if(setCounts.containsKey(arr[i])){
                setCounts.put(arr[i], setCounts.get(arr[i]) + 1);
            } else {
                setCounts.put(arr[i], 1);
            }
        }
        
        int max = 2;
        for(int key : setCounts.keySet()){
            int curr = setCounts.get(key);
            if(setCounts.containsKey(key - 1)){
                curr += setCounts.get(key - 1);
                max = Math.max(max, curr);
                curr -= setCounts.get(key - 1);
            }
            if(setCounts.containsKey(key+1)){
                curr += setCounts.get(key+1);
            }
            max = Math.max(max, curr);
        }
        return max;
    }
}