If 15 identical small cubes are put together to form a large cube, at least how many such small cubes are needed.
将15个相同的小正方体拼成一个大正方体，至少还需要多少个这样的小正方体．
<gadget id="calculator">3 ** 3</gadget>
<output>27</output>

<gadget id="calculator">27 - 15</gadget>
<output>12</output>

<result>12</result>