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+;; Ref:
+;; http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/fun_map.html
+;; https://stackoverflow.com/questions/47602677/recursive-factorial-function-in-common-lisp
+;; https://stackoverflow.com/questions/22522108/how-to-map-a-function-in-common-lisp
+;; https://stackoverflow.com/questions/1021778/getting-command-line-arguments-in-common-lisp
+;; https://riptutorial.com/common-lisp/example/8770/summing-a-list
+;; https://www.tutorialspoint.com/lisp/lisp_strings.htm
+
+(defun my-command-line ()
+  (or
+   #+CLISP *args*
+   #+SBCL *posix-argv*
+   #+LISPWORKS system:*line-arguments-list*
+   #+CMU extensions:*command-line-words*
+   nil))
+
+(defun range (min max &optional (step 1))
+  (when (<= min max)
+    (cons min (range (+ min step) max step))))
+
+(defun factorial (n)
+  (if (= n 1)
+      1
+    (* n (factorial (- n 1)))))
+
+(defun nth-root-of-five (x)
+  (if (= (mod x 5) 0)
+      (+ 1 (nth-root-of-five (/ x 5)))
+    0 ))
+
+(defun get-answer (n)
+  (let ((seq (range 1 n)))
+    (reduce '+ (map 'list #'nth-root-of-five (range 1 n)))))
+
+(defun show-divided-number(n prompt answer)
+  (let* ((str (write-to-string n))
+         (needle (- (length str) answer 1))
+         (str-left (subseq str 0 needle))
+         (str-right (subseq str (+ needle 1))))
+    (format t "~a~a | ~a~%" prompt str-left str-right)))
+
+(progn
+  (let* ((cmd-line (my-command-line))
+         (n (parse-integer (nth 1 cmd-line)))
+         (answer (get-answer n)))
+    (format t "N:  ~a~%" n)
+    (show-divided-number (factorial n) "N!: " answer)
+    (format t "~%Answer: ~a~%" answer)))