9.7. Find the maximum value of the expression $(\sqrt{9-\sqrt{7}} \sin x-\sqrt{2(1+\cos 2 x)}-1) \cdot(3+2 \sqrt{13-\sqrt{7}} \cos y-\cos 2 y)$. If the answer is not an integer, round it to the nearest integer.
Answer: 19. Instructions. Exact answer: $24-2 \sqrt{7}$.