Plant trees on both sides of a 100-meter sidewalk, how many trees need to be planted every 4 meters (both ends must be planted).
在100米的人行道两边栽树，每隔4米栽一棵(两端都要栽)需要栽多少棵树．
<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">25 + 1</gadget>
<output>26</output>

<gadget id="calculator">26 * 2</gadget>
<output>52</output>

<result>52</result>