Define a new operation whose rule is a*b=a**2-b**2, then (5*4)*2=how much.
定义一种新运算，其规则为a※b=a**2-b**2，则(5※4)※2=多少．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">25 - 16</gadget>
<output>9</output>

<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">81 - 4</gadget>
<output>77</output>

<result>77</result>