Plant willows on both sides of a 300-meter-long road, if one is planted every 15 meters. Moreover, both ends of the road must be planted. How many willow trees need to be planted in total?
在一条300米长的大路两边栽上柳树，如果每隔15米栽1棵．而且路的两端都要栽，一共需要栽多少棵柳树？
<gadget id="calculator">300 / 15</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>