In a six-story pagoda, the number of lamps lit on each floor is three times that of the one above it. It is known that 2 lamps are lit on the topmost floor. Find the total number of lamps lit in this tower.
一个六层塔，每一层点灯的盏数都是它的上一层的3倍，已知最顶层点了2盏灯，求这座塔共点了多少盏灯．
<gadget id="calculator">3 ** 6</gadget>
<output>729</output>

<gadget id="calculator">1 - 729</gadget>
<output>-728</output>

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

<gadget id="calculator">(-728) / (-2)</gadget>
<output>364</output>

<gadget id="calculator">2 * 364</gadget>
<output>728</output>

<result>728</result>