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();
        }
        Arrays.sort(a);
        int max=0,sum=0;
        boolean f=false;
        int last=a[0];
      int[] count= new int[100];
      for(int i:a)
        count[i]++;
      for(int i=1;i<100;i++){
        if(count[i-1]+count[i]>max)max=count[i-1]+count[i];
      }
        /*for(int i=1;i<n;i++){
          int x=a[i];
          if((f&& x>last)||x-last>1){
            f=false;sum=0;last=x;continue;
          }
          if(x==last)sum++;
          if(x-last<2){
            sum++; f=true;
          }
          max=sum>max?sum:max;
          last=x;
        }*/
      System.out.println(max);
      
          
    }
}