There are two towers with a distance of 140 meters, and a tree is planted every 20 meters between the two towers, how many trees should be planted in total?
有两座塔间距140米，两塔间每隔20米种一棵树，则共需种多少棵树．
<gadget id="calculator">140 / 20</gadget>
<output>7</output>

<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<result>6</result>