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 [] arr = new int [n];
        int [] count = new int [100];
        for (int i=0; i < n; i++){
            arr[i] = in.nextInt();
            count [--arr[i]]++;
        }
        int max=0;
        for (int i=0; i<99; i++){
            int f = count[i];
            int s = count[i+1];
            if ((f+s)>max)
                max=(f+s);
        }
        System.out.println (max);
    }
}