One pig is exchanged for 2 sheep, one sheep is exchanged for 3 rabbits, and one pig is exchanged for how many rabbits.
一头猪换2只羊，一只羊换3只兔子，一头猪换多少只兔子．
<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<result>6</result>