(defun tr-s (n)
  (let ((tr-str "abcdefghij"))
    (subseq tr-str n (+ n 1))))

(defun print-word (str n c)
  (if (= n c)
      (format t "~A~%" str)
      (loop as i
            below (+ c 1)
            do (print-word (concatenate 'string str (tr-s i)) n (+ c 1)))))

(print-word "a" (read) 1)