Plant trees on both sides of a road, every 10 meters (never plant at both ends), the road is 240 meters long, how many trees should be planted in total?
在一条马路的两侧种树，每隔10米种一棵(两端都不种)，这条马路全长240米，一共需种多少棵？
<gadget id="calculator">240 / 10</gadget>
<output>24</output>

<gadget id="calculator">24 - 1</gadget>
<output>23</output>

<gadget id="calculator">23 * 2</gadget>
<output>46</output>

<result>46</result>