using System;

public class Program

{

    public static void Main()

    {

        int Numero = 0;

        int refBASE = 26;

        string refReturn = string.Empty;

        int refReference = Numero - 65;

            while(refReference < refBASE) 

            {

                refReturn += (char)(65 + (refReference - refBASE * (int)(refReference / refBASE)));

                refReference = (int)(refReference / refBASE) - 1;

            }

​

            refReturn += (char)(refReference + 65);

​

            Console.WriteLine(refReturn);

    }

}