A road is 1 km long, and a street lamp is installed every 50 meters on both sides of the road (both ends are installed), how many street lamps need to be installed in total.
一条路长1千米，在路的两侧每隔50米安装一盏路灯(两端都安)，一共需要安装路灯多少盏．
<gadget id="calculator">1_000 / 50</gadget>
<output>20</output>

<gadget id="calculator">1 * 20</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>