If a sheep is tied to the middle of the grass with a 5-meter-long rope, what is the range that the sheep can eat the grass?
把一只羊用5米长的绳子系在草地中间，这只羊能吃到青草的范围是多少？
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>