There is a 5-layer hollow phalanx with 240 people lined up, and how many more people are added inside can make the phalanx into a 6-layer hollow phalanx.
有一个240人排成的5层空心方阵，再增加多少人在内部，就可以使该方阵变成一个6层空心方阵．
<gadget id="calculator">240 / 4 / 5</gadget>
<output>12</output>

<gadget id="calculator">12 + 5</gadget>
<output>17</output>

<gadget id="calculator">17 - 2 - 2 - 2 - 2 - 2</gadget>
<output>7</output>

<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<result>24</result>