Use a 24-meter-long bamboo fence to form a rectangular or square chicken pen with the help of a wall. What is the maximum area in square meters?
用24米长的竹篱笆，借助一面墙壁围成一个长方形或正方形鸡栏，面积最大是多少平方米．
<gadget id="calculator">2 + 2</gadget>
<output>4</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<gadget id="calculator">2 * 6 * 6</gadget>
<output>72</output>

<result>72</result>