For a pile of bricks, half of the total number is removed for the first time, 3 more than the remaining half for the second time, 3 less than the remaining half for the third time, and 15 bricks are left in the end.
一堆砖，第一次搬走总数的一半，第二次搬走剩下的一半多3块，第三次搬走剩下的一半少3块，最后剩下15块，原来一共多少块．
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">24 + 3</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<gadget id="calculator">54 * 2</gadget>
<output>108</output>

<result>108</result>