The duckweed in a pool grows twice as fast as the previous day. On the 15th day, the duckweed only covers half of the pool. How many days will it take to cover the entire pool?
一个水池中的浮萍每天生长速度是前一天的一倍，第15天时浮萍才长满了半池，长满整个池要多少天．
<gadget id="calculator">15 + 1</gadget>
<output>16</output>

<result>16</result>