In a square piece of paper with a circumference of 80 cm, the largest circle is to be cut out. What is the circumference of this circle in cm?
在一个周长为80厘米的正方形纸片内，要剪一个最大的圆，这个圆周长是多少厘米．
<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<gadget id="calculator">3.14 * 20</gadget>
<output>62.8</output>

<result>62.8</result>