For nine street lamps numbered 1, 2, 3...9 on a road, in order to save electricity, you can turn off three of them, but you cannot turn off two or three adjacent lights at the same time. How many lamp methods are there?
一条马路上编号为1、2、3…9的九盏路灯，为了节约用电，可以把其中的三盏关掉，但不能同时关掉相邻的两盏或三盏，则所有不同的关灯方法有多少种？
<gadget id="calculator">7 * 6 * 5</gadget>
<output>210</output>

<gadget id="calculator">3 * 2 * 1</gadget>
<output>6</output>

<gadget id="calculator">210 / 6</gadget>
<output>35</output>

<result>35</result>