There is a sheep tied to a stake in the grass. The length of the rope is 4 meters. How many square meters of grass can the sheep eat at most?
有一只羊栓在草地的木桩上，绳子的长度是4米，这只羊最多可以吃到多少平方米的草？
<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

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

<result>50.24</result>