(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((n (read))
         (alphabet "abcdefghijklmnopqrstuvwxyz"))
    (dotimes (a 26)
      (dotimes (b 26)
        (dotimes (c 26)
          (dotimes (d 26)
            (if (< (+ (* 26 26 26 a) (* 26 26 b) (* 26 c) d) (1- n))
                (progn (write-char #\a)
                       (write-char (aref alphabet a))
                       (write-char (aref alphabet b))
                       (write-char (aref alphabet c))
                       (write-char (aref alphabet d))
                       (write-char #\a)
                       (terpri))
                (return))))))
    (format t "an~%")))

(main)