A small movie hall has 10 rows of seats, the first row has 12 seats, and from the second row onwards, each row has one more seat than the first row. How many seats are there in this cinema hall?
一个小电影厅有10排座位，第1排的座位有12个，从第2排起，每排座位都比前1排多1个．这个电影厅共有座位多少个．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 1</gadget>
<output>9</output>

<gadget id="calculator">12 + 9</gadget>
<output>21</output>

<gadget id="calculator">12 + 21</gadget>
<output>33</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">33 * 5</gadget>
<output>165</output>

<result>165</result>