If the circumference of a circle is 12.56 cm and the radius is 2 cm, what is the area in square centimeters?
一个圆的周长是12.56厘米，半径是2厘米，面积是多少平方厘米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<result>12.56</result>