(define (merge list1 list2)
   (cond ((null? list1) list2) 
         ((null? list2) list1)
         ((< (car list1)(car list2))
          (cons (car list1)(merge (cdr list1) list2)))
         (#t (cons (car list2)(merge list1 (cdr list2))))))

; merge sort
(define (sort lst)
  (cond ((null? lst) lst)
        (else (merge (list (car lst)) (sort (cdr lst))))))


(sort (list 4 3 2 1))