The distance between the library and the science and technology museum is 120 meters. The greening team will plant trees on both sides of the path between the two museums (none at both ends). The distance between two adjacent trees is 3 meters. How many trees will be planted in total?
图书馆和科技馆之间相距120米，绿化队要在两馆间的小路两旁栽树(两头都不栽)，相邻两棵树之间的距离是3米，一共要栽多少棵树？
<gadget id="calculator">120 / 3</gadget>
<output>40</output>

<gadget id="calculator">40 - 1</gadget>
<output>39</output>

<gadget id="calculator">39 * 2</gadget>
<output>78</output>

<result>78</result>