using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        new Magatro().Solve();
    }
}

public class Magatro
{
    private int N, D;
    public void Solve()
    {
        string[] s = Console.ReadLine().Split(' ');
        N = int.Parse(s[0]);
        D = int.Parse(s[1]);
        if (N >= D)
        {
            Console.WriteLine(new string('A', D) + new string('C', N - D));
        }
        else
        {
            Console.WriteLine(new string('A', 2 * N - D) + new string('B', D - N));
        }
    }
}