There are 20 seats in a row in the cinema. Xiao Hua and Xiao Ming are twins, let them sit together, and Xiao Hua is on Xiao Ming's right. How many different ways of sitting are there in the same row?
电影院里一排有20个座位．小华和小明是双胞胎，要让他俩坐在一起，并且小华在小明的右边．在同一排有多少种不同的坐法？
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<result>19</result>