Uncle Zhang wants to surround a garden with a length of 18 meters and a width of 9 meters. What is the minimum length of the fence?
张叔叔要围一个靠墙的长为18米，宽为9米的花园，最少要多长的篱笆？
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

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

<result>36</result>