On the grass, a sheep is tied by a rope 4 meters long. How much grass can this sheep eat at most?
草地上，一只羊被一根长为4米的绳子拴着．这只羊最多可以吃到多大面积的草？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<result>50.24</result>