On the side of the path, 31 trees are planted from the beginning to the end, and one tree is planted every 2 meters. What is the total length of the path in meters?
在小路的一旁从头到尾种了31棵树，每隔2米种一棵，这条小路全长是多少米．
<gadget id="calculator">31 - 1</gadget>
<output>30</output>

<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<result>60</result>