Plant trees on one side of a road from the beginning to the end, plant a tree every 15 meters, and plant a total of 41 trees. How long is this road in meters?
在一条路的一侧从头到尾种树，每隔15米种一棵树，共种41棵，这条路长多少米？
<gadget id="calculator">41 - 1</gadget>
<output>40</output>

<gadget id="calculator">40 * 15</gadget>
<output>600</output>

<result>600</result>