using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var limit = 13;

        for(int i =0; i < limit; i++)

         {                                  

            if(i%3 == 1 && i+1 < limit){

                Console.WriteLine($"<div open>");

            }

            Console.WriteLine($"int = {i} -----  power 3 = {i%3} ----");

            if(i%3 == 2){

                Console.WriteLine($"<div close>");

            }

         }

​

    }

}