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(defun append-find (l1 l2 lres) (cond ((eq l1 '?)(cond ((and (not(equal l2 (cdr lres))) (not(equal lres NIL))) (cons (car lres) (append-find '? l2 (cdr lres)))) ((equal (cdr lres) l2) (cons (car lres) '())) (t '(the lists introduced are incompatible)))) ((eq l2 '?) (if (equal l1 NIL) (prin1 lres) (cond ((equal (car l1) (car lres)) (append-find (cdr l1) '? (cdr lres))) (t '(the lists introduced are incompatible))))) (t (append l1 l2))))

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