The perimeter of a square piece of paper is 16 centimeters. Cut out the largest circle inside the square. What is the perimeter of the circle in centimeters?
一个正方形纸片的周长是16厘米，在这个正方形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>