(defn smallest-divisor [n]
  (defn square [n]
    (* n n))
  (defn divides? [a b]
    (= (mod b a) 0))
  (defn iter [n test]
    (cond
      (> (square test) n) n
      (divides? test n) test
      (iter n (+ test 1))))
  (iter n 2))

(trace (smallest-divisor 199))
(print (smallest-divisor 1999))
(print (smallest-divisor 19999))