There are 10 bus stops including the starting station and the terminal station. If a bus departs from the starting station, except for the terminal station, there will be exactly one passenger who gets on the bus at each station and get off from this station to every subsequent station. What is the minimum number of seats the car needs in order for every passenger to have a seat?
有一路公共汽车，包括起点站和终点站在内共10个停车点．如果一辆公共汽车从起点站开出，除终点站外，每一站上车的乘客中恰好各有一位从这一站到以后的每一站下车．为了使每位乘客都有座位，那么这辆车至少需要多少个座位？
<gadget id="calculator">9 + 8 + 7 + 6 + 5</gadget>
<output>35</output>

<gadget id="calculator">0 + 1 + 2 + 3 + 4</gadget>
<output>10</output>

<gadget id="calculator">35 - 10</gadget>
<output>25</output>

<result>25</result>