;(mod (tree)
;    (defun sum (tree)
;        (if (l tree) (+ (sum (f tree)) (sum (r tree))) tree)
;    )
;    (sum tree)
;)

(a (q 2 2 (c 2 (c 5 (q)))) (c (q 2 (i (l 5) (q 16 (a 2 (c 2 (c 9 (q)))) (a 2 (c 2 (c 13 (q))))) (q . 5)) 1) 1))