A sheep is tied with a 2m long rope under a tree, how many square meters of grass can the sheep eat?
在一棵树下用2m长的绳子拴着一只羊，这只羊可以吃到多少平方米的草？
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>