(format t "----- basic math -----")
(defvar a 5)
(defvar b 2)
(defvar c)
(format t "~%Variable A = ~d" a)
(format t "~%Variable B = ~d" b)
(format t "~%Variable C is undefined")
(format t "~%~%What should we do with it?")
(format t "~%1. ~d+~d" A B)
(format t "~%2. ~d-~d" A B)
(format t "~%3. ~d-~d" B A)
(format t "~%4. ~d*~d" A B)
(format t "~%5. ~d/~d" A B)
(format t "~%6. ~d/~d" B A)
(format t "~%7. ~d%~d" A B)
(format t "~%8. ~d%~d" B A)
(format t "~%9. ~d^~d" A B)
(format t "~%10. ~d^~d" B A)
(format t "~%~%Your choice: ")
(defvar choice (read))

(if (= choice 1)
  (defvar c (+ A B))
  )

(if (= choice 2)
  (defvar c (- A B))
  )

(if (= choice 3)
  (defvar c (- B A))
  )

(if (= choice 4)
  (defvar c (* A B))
  )

(if (= choice 5)
  (defvar c (/ A B))
  )

(if (= choice 6)
  (defvar c (/ B A))
  )

(if (= choice 7)
  (defvar c (mod A B))
  )

(if (= choice 8)
  (defvar c (mod B A))
  )

(if (= choice 9)
  (defvar c (expt A B))
  )

(if (= choice 10)
  (defvar c (expt B A))
  )

(format t "C = ~d" (float c))