There is a bus, including the starting point and the terminal station, there are 15 stations in total. If there is a car, except for the terminal station, among the passengers who get on the bus at each station, there is exactly one passenger from this station to each subsequent station. In order for every passenger to have a seat, what is the minimum number of seats the bus must have?
有一路公共汽车，包括起点和终点站在内，共有15个车站．如果有一辆车，除终点站外，每一站上车的乘客中，恰好各有一位乘客从这一站到以后的每一站．为了使每位乘客都有座位，问这辆公共汽车至少要有多少个座位？
<result>56</result>