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

public class Program
{
    public static void Main() {
        var so = new Solver();
        so.Solve();
    }
}

public class Solver
{
    private readonly Reader reader;
    private readonly TextWriter writer;

    public Solver() {
        reader = new Reader(Console.In);
        writer = Console.Out;
    }

    public Solver(string input, string  output) {
        reader = new Reader(new StreamReader(input));
        writer = new StreamWriter(output);
    }

    public void Solve() {
        int N = reader.RInt();
        int D = reader.Int();

        int ana = 0;
        string ans = "";
        for (int i = 0; i < N; i++) {
            if (ana == D) {
                ans += "C";
            } else if (ana + (N - i) * 2 == D) {
                ans += "B";
                ana += 2;
            } else {
                ans += "A";
                ana++;
            }
        }

        writer.WriteLine(ans);
        writer.Flush();
    }
}

public class Reader
{
    private readonly TextReader reader;
    private readonly char separator = ' ';
    private string[] A = new string[0];
    private int i;

    public Reader(TextReader r) {
        reader = r;
    }

    public string String() { return Set(); }
    public int Int() { return int.Parse(Set()); }
    public long Long() { return long.Parse(Set()); }
    public decimal Decimal() { return decimal.Parse(Set()); }

    public string RString() { return RSet(); }
    public int RInt() { return int.Parse(RSet()); }
    public long RLong() { return long.Parse(RSet()); }
    public decimal RDecimal() { return decimal.Parse(RSet()); }

    public int[] IntArray() { return A.Select(x => int.Parse(x)).ToArray(); }

    private void Read() {
        string line = reader.ReadLine();

        A = line.Split(separator);
        i = 0;
    }

    private string Set() { return A[i++]; }
    private string RSet() { Read(); return A[i++]; }
}