In a square paper with a circumference of 80 cm, cut a largest circle, what is the area of the cut circle in square centimeters?
在一张周长80cm的正方形纸内，剪一个最大的圆，所剪圆的面积是多少平方厘米．
<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<result>314</result>