import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int d = sc.nextInt();
        if (d > n) {
            int b = d - n;
            char[] bstr = new char[b];
            Arrays.fill(bstr, 'B');
            char[] astr = new char[n - b];
            Arrays.fill(astr, 'A');
            System.out.print(astr);
            System.out.println(bstr);
        } else {
            int c = n - d;
            char[] cstr = new char[c];
            Arrays.fill(cstr, 'C');
            char[] astr = new char[n - c];
            Arrays.fill(astr, 'A');
            System.out.print(astr);
            System.out.println(cstr);
        }
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}