There are 20 street lamps on one side of Shengli Street (not installed at both ends), and the distance between every two lamps is 10 meters. What is the total length of Victory Street?
胜利街的一边有20盏路灯(两头不装)，每两盏灯之间相隔10米．胜利街全长是多少米？
<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 10</gadget>
<output>210</output>

<result>210</result>