There is a road in front of the school, and a tree is planted every 2 meters on the side. A total of 22 trees are planted from the beginning to the end. How long is this road?
在学校的前面有一条公路，在一旁每隔2米植一棵树，从起点到终点一共植了22棵树，这条公路长多少米？
<gadget id="calculator">22 - 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>