The distance between the two buildings is 60 meters, and a magnolia flower is planted every 3 meters (planted in a row, without planting at both ends), how many trees were planted in total.
两座楼房之间相隔60米，每隔3米栽一棵玉兰花(栽一排，两端都不栽)，共栽了多少棵．
<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<result>19</result>