The distance between the school teaching building and the dormitory building is 72m. The school needs to plant trees between the two buildings, one tree every 4m. How many trees should be planted in total?
学校教学楼与宿舍楼之间相距72m，学校要在两栋楼房之间栽树，每隔4m栽一棵，一共要栽多少棵树．
<gadget id="calculator">72 / 4</gadget>
<output>18</output>

<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<result>17</result>