using System.Collections.Generic;
using System;

public class Hello
{
    public static void Main()
    {
        var ans = new List<string>();
        string[] line = Console.ReadLine().Trim().Split(' ');
        var n = int.Parse(line[0]);
        var d = int.Parse(line[1]);
        var a = 0;   var c = 0;
        var bmax = 2 * n - d;
        for (int i = 0; i <= bmax; i++)
        {
            if ((bmax - i) % 2 == 0) c = (bmax - i) / 2;
             a = n - i - c;
            if (a>= 0) ans.Add(getString(a, i, c));
        }
        ans.Sort();
        Console.WriteLine(ans[0]);
    }
    public static string getString(int a, int b, int c) => new string('A', b) + new string('B', a) + new string('C', c);
}