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

class P
{
    static void Main(string[] _)
    {
        _ = Console.ReadLine().Split(' ');
        int N = int.Parse(_[0]);
        int D = int.Parse(_[1]);
        int b = D - N;
        int c = N - D;
        StringBuilder r = new StringBuilder();
        for (int i = 0; i < N; i++)
        {
            r.Append("A");
        }

        if (b > 0)
        {
            for (int i = N - 1; i >= N - b; i--)
            {
                r[i] = 'B';
            }
        }
        else if (c > 0)
        {
            for (int i = N - 1; i >= N - c; i--)
            {
                r[i] = 'C';
            }
        }


        Console.WriteLine(r);
    }
}