On both sides of a road 800 meters long, plant a row of trees with a distance of 4 meters. How many trees are needed in total?
在一条长800米的公路两侧，各栽一行树，树的株距是4米．共需多少棵树？
<gadget id="calculator">800 / 4</gadget>
<output>200</output>

<gadget id="calculator">200 + 1</gadget>
<output>201</output>

<gadget id="calculator">201 * 2</gadget>
<output>402</output>

<result>402</result>