Description:
Let $$$a, b, c, d$$$ be real numbers such that $$$a=\sqrt{7-\sqrt{6-a}}$$$, $$$b=\sqrt{7-\sqrt{6+b}}$$$, $$$c=\sqrt{7+\sqrt{6-c}}$$$ and $$$d=\sqrt{7+\sqrt{6+d}}$$$. Compute the product $$$abcd$$$.
Input Format:
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Output Format:
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Note:
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