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();
        char[] ans = new char[n];
        if (n >= d) {
            for (int i = 0; i < n; i++) {
                if (i < d) {
                    ans[i] = 'A';
                } else {
                    ans[i] = 'C';
                }
            }
        } else {
            for (int i = 0; i < n; i++) {
                if (i < n * 2 - d) {
                    ans[i] = 'A';
                } else {
                    ans[i] = 'B';
                }
            }
        }
        System.out.println(ans);
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    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();
    }
    
}