A sheep is tied to a tree stump to graze. The rope is 4 meters long. How much grass can this sheep eat?
一只羊栓在树桩上吃草，绳长4米，这只羊能吃到多大面积的草？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<result>50.24</result>