What is the unit digit obtained by subtracting 9 from the product of 100 multiplications of 2?
100个2连乘的积减去9，所得的个位数字是多少．
<gadget id="calculator">1 * 2 * 1 * 2 * 1 * 2 * 1 * 2</gadget>
<output>16</output>

<gadget id="calculator">16 - 9</gadget>
<output>7</output>

<result>7</result>