using System.Numerics;

public class Program
{
    public static void Main()
    {

        //BigInteger num = BigInteger.Parse(Console.ReadLine() ?? string.Empty);
        //int num = int.Parse(Console.ReadLine() ?? string.Empty);
        string[] moji = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string moji = Console.ReadLine() ?? string.Empty;

        int length = int.Parse(moji[0]);
        int holl = int.Parse(moji[1]);

        if(holl ==0)
        {
            for(int i = 0;i < length;i++)
            {
                Console.Write("C");
            }
            Console.WriteLine();
            return;
        }
        else if(holl /2 == length)
        {
            for (int i = 0;i < length;i++)
            {
                Console.Write("B");
            }
            Console.WriteLine();
            return;
        }
        else if (length + 1 == holl)
        {
            for (int i = 0; i < length - 1; i++)
            {
                Console.Write("A");
            }
            Console.WriteLine("B");
            return;
        }
        else if (length - 1 == holl)
        {
            for (int i = 0; i < length - 1; i++)
            {
                Console.Write("A");
            }
            Console.WriteLine("C");
            return;
        }
        else
        {
            for (int i = 0; i < length; i++)
            {
                Console.Write("A");
            }
            Console.WriteLine();
        }

    }
}