Xiaohong has a rectangular handkerchief with a length of 5 decimeters and a width of 4 decimeters. Now she wants to put lace around the handkerchief. How long does she want to buy?
小红有一块长方形的手帕，长5分米，宽4分米，她现在要在手帕的四周镶上花边，要购买多长的花边？
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

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

<result>18</result>