There are 18 seats in a row in the auditorium. Zhang Ming and Zhang Yang are twins. Let them sit together, and Zhang Ming sits on the left of Zhang Yang. How many different ways are there in the same row?
礼堂里一排有18个座位，张明和张扬是双胞胎，让他俩坐在一起，并且张明坐在张扬的左边，在同一排有多少种不同的坐法．
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<result>17</result>