After the No. 8 bus departs from the departure station, it needs to pass through 6 stations before arriving at the destination. How many types of tickets do you need to prepare?
8路公共汽车从始发站开出后，中间要经过6个车站，才到终点，它需要准备多少种车票．
<gadget id="calculator">7 + 6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>28</output>

<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<result>56</result>