If the circumference of an ancient tree is 314 cm, what is the area of its cross section?
一棵古树的周长是314厘米，则它的横截面的面积是多少？
<gadget id="calculator">314 / 3.14 / 2</gadget>
<output>50</output>

<gadget id="calculator">50 ** 2</gadget>
<output>2_500</output>

<gadget id="calculator">3.14 * 2_500</gadget>
<output>7_850</output>

<result>7_850</result>