How many small cubes with side length 1cm are assembled to form a large cube with side length 3cm.
棱长1cm的小正方体拼成一个棱长3cm的大正方体，需要用这样的小正方体多少个．
<gadget id="calculator">3 * 3 * 3</gadget>
<output>27</output>

<result>27</result>