In a rectangle with a length of 4.2 cm and a width of 4 cm, cut a circle as large as possible. What is the circumference of this circle?
在一个长4.2cm，宽4cm的长方形中，剪一个尽可能大的圆，这个圆的是周长是多少．
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>