If the clock strikes 2 times at 2 o'clock, it takes 2 seconds to finish the knocking; then 6 times at 6 o'clock, it takes how many seconds to finish the knocking.
时钟2点敲2下，2秒钟敲完；那么6点敲6下，多少秒钟敲完．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<result>10</result>