What is the area of a circle surrounded by 12.56 meters of iron wire?
用12.56米的铁丝围成一个圆，圆的面积是多少．
<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>