The diameter of a semicircular flower bed is 8 meters, and now it is surrounded by a fence, how many meters of fence is needed at least.
一个半圆形花坛的直径是8米，现在用篱笆将它围起来，至少需要多少米篱笆．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

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

<gadget id="calculator">12.56 + 8</gadget>
<output>20.56</output>

<result>20.56</result>