There are 5 train stations between A and B of Xingan Railway (including A and B stations). How many different train tickets should the ticket center prepare?
新干铁路A、B两地间共有5个火车站(包括A、B两站)，票务中心要准备多少种不同的火车票？
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>