There is an automatic rotating sprinkler with a range of 4 meters. What is the maximum area it can spray?
有一种自动旋转喷水龙头，射程是4米，它能喷洒的最大面积是多少．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>