A fence is surrounded by a rectangle with a length of 84 meters and a width of 56 meters. How many meters is the fence?
在一个长84米、宽56米的长方形四周围一圈篱笆，篱笆长多少米？
<gadget id="calculator">84 + 56</gadget>
<output>140</output>

<gadget id="calculator">140 * 2</gadget>
<output>280</output>

<result>280</result>