(DEFUN FIRST_EL(n lst)
 (COND (( < = n 0) NIL)
       ((NULL lst) NIL)
       (1 (CONS (CAR lst) (FIRST_EL (- n '1) (CDR LST))))
 )
)

(DEFUN LAST_EL(n lst)
 (COND ((<= n 0) LST)
       ((NULL lst) NIL)
       (1 (LAST_EL (- n '1) (CDR LST)))
 )
)

(DEFUN SPLIT(lst)
 (SET 'fi (FIRST_EL (/ (LENGTH lst) 2) lst))
 (SET 'li (LAST_EL  (LENGTH fi) lst))
 (LIST fi li)
)

(DEFUN MERGE(lst1 lst2)
 (COND ((NULL lst1) lst2)
       ((NULL lst2) lst1)
       ((> (CAR lst1) (CAR lst2)) (CONS (CAR lst2) (MERGE lst1 (CDR lst2))))
       (1 (CONS (CAR lst1) (MERGE (CDR lst1) lst2)))
 )
)

(DEFUN SORT(LST)
 (COND ( (eq (LENGTH (CAR (SPLIT LST))) 1) (MERGE (CAR (SPLIT LST)) (CAR(CDR (SPLIT LST)))))
       ( 1 (MERGE (SORT (CAR (SPLIT LST))) (SORT(CAR (CDR (SPLIT LST))))))
 )
)