There are 5 stations C, D, E, F, and G between A and B. How many different ticket samples can be sold between A and B?
从A地到B地中间一共有C、D、E、F、G5个站，则AB两地之间一共能卖多少种不同的票样．
<gadget id="calculator">6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>