There are 18 stations in the route of bus No. 18 (the end is not connected), and each phase leads to two stations separated by 1 kilometer. How many kilometers is the total length of this route?
18路公交车行驶路线(首尾不连)中共有18个站，每相领两站相隔1千米，这条路线全长多少千米？
<gadget id="calculator">1 * 1</gadget>
<output>1</output>

<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<result>17</result>