A rectangle with a perimeter of 72 meters and its length and width are integers, what is its maximum area?
一个周长是72米的长方形，它的长、宽都是整米数，它的最大面积是多少．
<gadget id="calculator">72 / 2</gadget>
<output>36</output>

<gadget id="calculator">36 / 2</gadget>
<output>18</output>

<gadget id="calculator">18 * 18</gadget>
<output>324</output>

<result>324</result>