A rectangular tablecloth with a length of 5 decimeters and a width of 4 decimeters is sewed with lace around the tablecloth. What is the minimum length of lace?
一块长方形的桌布，长5分米，宽4分米，在桌布的四周缝上花边，至少需要多长的花边？
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>