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[] counts = new int[100];
        int max = 0;
        for(int a_i=0; a_i < n; a_i++){
            int temp = in.nextInt();
            counts[temp]++;
            max = temp > max ? temp : max;
        }
        int highest = 0;
        for (int i = 0; i<max;i++){
            int temp = counts[i]+counts[i+1];
            highest = temp>highest? temp : highest;
        }
        System.out.println(highest);
    }
}