20 small flags are inserted on both sides of the welcome road (both ends), and the distance between two adjacent small flags is 10 meters. How many meters is this welcome road?
20面小旗插在迎宾道路的两旁(两端都插)，每相邻两面小旗的距离是10米．这条迎宾道长多少米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 10</gadget>
<output>90</output>

<result>90</result>