Cut out the largest circle in a square cardboard with a circumference of 16 cm. What is the circumference of this circle in cm?
在一个周长是16厘米的正方形纸板内剪下一个最大的圆，这个圆的周长是多少厘米．
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

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

<result>12.56</result>