If the diameter of a semicircular flower bed is 4 meters, what is the perimeter of the flower bed in meters?
一个半圆形花坛的直径是4米，则这个花坛的周长是多少米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">6.28 + 4</gadget>
<output>10.28</output>

<result>10.28</result>