(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((n (read))
         (d (read)))
    (if (< n d)
        (format t "~a~a~%" (make-string (- (* 2 n) d) :initial-element #\A) (make-string (- d n) :initial-element #\B))
        (format t "~a~a~%" (make-string d :initial-element #\A) (make-string (- n d) :initial-element #\C)))))

(main)