The chicken coop built against the wall forms a semicircle with a diameter of 80 meters. How many meters of fence are needed to build this chicken coop?
依墙而建的鸡舍围成半圆形，其直径是80米，建成这个鸡舍需要多少米篱笆？
<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">3.14 * 40</gadget>
<output>125.6</output>

<result>125.6</result>