2 sheep = 1 pig, 4 pigs = 1 cow, 2 cows = how many sheep.
2只羊=1头猪，4头猪=1头牛，2头牛=多少只羊．
<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">2 * 8</gadget>
<output>16</output>

<result>16</result>