To surround a rectangular photo frame with a length of 18 decimeters and a width of 10 decimeters, how many decimeters of ribbons are needed?
要给一个长18分米，宽10分米的长方形的相框围上彩带，请问需要多少分米的彩带？
<gadget id="calculator">18 + 10</gadget>
<output>28</output>

<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<result>56</result>