Plant trees between two buildings 120 meters apart, and plant one tree every 20 meters. How many trees were planted in total?
在相距120米的两楼之间种树，每隔20米种一棵，共栽了多少棵．
<gadget id="calculator">120 / 20</gadget>
<output>6</output>

<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<result>5</result>