import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt(), D = sc.nextInt();
        sc.close();
        if (N > D) {
            for (int i = 0; i < D; ++i) System.out.print("A");
            for (int i = 0; i < N - D; ++i) System.out.print("C");
        }
        else {
            for (int i = 0; i < 2 * N - D; ++i) System.out.print("A");
            for (int i = 0; i < D - N; ++i) System.out.print("B");
        }
    }
}