There is a circular fountain in the park with a circumference of 31.4 meters. What is the area of this fountain?
公园里有一个圆形喷水池，周长是31.4米．这个喷水池的面积是多少？
<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

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

<result>78.5</result>