There is a sprinkler head on the grass, which can spray up to 2 meters. How much lawn can the sprinkler head rotate for one revolution?
草地上有一个喷水头，最远能喷2米，喷水头转动一周能浇多大面积的草坪？
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>