(define (square n)
  (* n n))

(define (smallest-divisor n)
  (find-divisor n 2))

(define (find-divisor n test-divisor)
  (define (next iterator)
    (if (= iterator 2) 3 (+ iterator 2)))
  
  (cond ((> (square test-divisor) n) n)
        ((divides? test-divisor n) test-divisor)
        (else (find-divisor n (next test-divisor)))))
; find-divisor

(define (divides? a b)
  (= (remainder b a) 0))

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