There is a 21-meter-long path between two buildings. On one side of the path, a tree is placed every 3 meters. How many trees should be carried?
两幢楼中间有一条长21米的小路，在小路的一边每隔3米载一棵树，要载多少棵树．
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<result>6</result>