There is a semicircular flower bed with a diameter of 18m. It is planned to surround the flower bed with an iron fence. How long is the iron fence?
有一个直径是18m的半圆形花坛，计划在花坛的周围围一圈铁栅栏，这条铁栅栏长是多少米？
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<gadget id="calculator">28.26 + 18</gadget>
<output>46.26</output>

<result>46.26</result>