The circumference of a circle is 12.56 centimeters, what is its area in square centimeters.
一个圆的周长是12.56厘米，它是面积是多少平方厘米．
<gadget id="calculator">12.56 / 3.14 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

<result>12.56</result>