Install street lamps on both sides of a road with a length of 1000 meters, and install a street lamp every 50 meters, how many street lamps are installed in total?
在一条长1000米的公路两旁安装路灯，每隔50米安装一盏路灯，共安装多少盏路灯．
<gadget id="calculator">1_000 / 50</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>