There are 18 seats in a row in the auditorium. If A and B want to sit in the same row of adjacent seats, how many different ways can they sit?
礼堂里一排有18个座位，如果甲乙要坐在同一排相邻的座位上，他们共有多少种不同的坐法．
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">17 * 2</gadget>
<output>34</output>

<result>34</result>