A caterpillar grows to an adult and doubles in size every day. On the 10th day, it grows to 10 cm. When it grows to 20 cm, what day is it?
一条毛毛虫长到成虫，每天长一倍，第10天长到了10厘米，长到20厘米时是第多少天．
<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>