On one side of the road, red flags should be inserted at intervals of 1 meter, 2 meters, 4 meters, 7 meters, 11 meters, and how many meters should be inserted immediately behind.
在马路一边按隔1米、2米、4米、7米、11米…插红旗，紧更后面应该多少米插红旗．
<gadget id="calculator">11 + 5</gadget>
<output>16</output>

<result>16</result>