Arrange 9 small flags in a row with 2 meters between each two sides. How many meters are there from side 1 to side 9?
把9面小旗排成一排，每两面之间空2米．第1面到第9面，共多少米．
<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>