Plant a cypress tree every one meter around a circular flower bed, plant a total of 20 trees, what is the circumference of the flower bed in meters?
绕圆形花坛一周每隔一米种一棵柏树，共种了20棵，花坛周长为多少米．
<gadget id="calculator">1 * 20</gadget>
<output>20</output>

<result>20</result>