using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var result = IntegerToBase26String(27);

        Console.WriteLine(result);

    }

    public static string IntegerToBase26String(int number)

    {

        int quotient = number;

        List<char> result = new List<char>();

        while (quotient > 0) {

            quotient = Math.DivRem(quotient, 26, out int remainder);

            result.Add((char)('A' + remainder));

        }

        return new String(result.ToArray());

    }

}