Obviously, there are 2 story books on the A floor of the bookshelf, and 3 science and technology books on the B floor. There are several different ways to arrange these books.
明明在书架的A层摆了2本故事书，在B层摆放了3本科技书，这些书有几种不同的摆法．
<gadget id="calculator">3 * 2 * 1</gadget>
<output>6</output>

<gadget id="calculator">2 * 6</gadget>
<output>12</output>

<result>12</result>