A semicircular lawn with a radius of 10 meters is planned to surround it with a fence. What is the minimum length of the fence?
一个半径为10米的半圆形草坪，计划在它的周围围一圈篱笆，篱笆至少长多少米？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 2 * 5</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 + 10</gadget>
<output>41.4</output>

<result>41.4</result>