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[] mas = new int[101];

        
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            
            mas[a[a_i]]++;
        }
        
        in.close();
        
     
        int maxNum  = 0;
        
        //ni = 0;
        
        for (int mi = 0; mi < 100; mi++) {
            int tmp = mas[mi] + mas[mi+1];
            if (tmp > maxNum) {
                maxNum = tmp;
            }
        }
        
        System.out.println(maxNum);
        
    }
}