There are 15 stations on a certain bus line (including the starting point and the ending point). Among the people who get on the train at each station, exactly one will get off at each station in the future. To ensure that every passenger has a seat during driving, how many seats should there be at least for passengers?
某公共汽车线路上共有15个站(包括起点和终点站)．在每个站上车的人中，恰好在以后各站分别下去一个．要使行驶过程中每位乘客均有座位，车上至少备有多少个座位供乘客使用？
<gadget id="calculator">8 * 7</gadget>
<output>56</output>

<result>56</result>