(defun sum-list (a)
    (cond
        ((NULL a) 0)
        (T (+ (CAR a) (sum-list (CDR a))))
    )
)

(defun sum-pair (a)
    (cond
        ((NULL a) NIL)
        (T (cons (sum (CAR a)) (sum-pair (CDR a))))
    )
)

(defun max-list (a)
    (cond
        ((NULL a) NIL)
        ((NULL (CDR a)) (CAR a))
        ((> (CAR a) (max-list (CDR a))) (CAR a))
        (T (max-list (CDR a)))
    )
)

(defun pn-sum (a)
    (cond
        ((NULL a) '(0 0))
        (T
            (LIST
                (+ (cond ((> (CAAR a) 0) (CAAR a)) (T (CADAR a))) (CAR (pn-sum (CDR a))))
                (+ (cond ((< (CAAR a) 0) (CAAR a)) (T (CADAR a))) (CADR (pn-sum (CDR a))))
            )
        )
    )
)

(print (pn-sum '((1 -1) (3 -2) (-3 6) (0 3))))