On a section of road 20 meters long, plant a pine tree every 4 meters. If both ends are planted, how many pine trees are needed in total?
在20米长的一段公路上，每隔4米栽一棵松树．如果首尾都栽，一共需要多少棵松树．
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

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

<result>6</result>