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];
        
        int[] w = new int[101];
        
        for(int a_i=0; a_i < n; a_i++){
            int i = in.nextInt();
            w[i]++;
        }
        
        int res = 0;
        for (int i = 0; i < 100; ++i) {
            res = Math.max(res, w[i] + w[i + 1]);
        }
        System.out.println(res);
    }
}