using System;

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