Install street lamps on both sides of a street with a total length of 2 kilometers (both ends must be installed), one every 50 meters, how many street lamps should be installed in total.
在一条全长2千米的街道两旁安装路灯(两端也要安装)，每隔50米安一座，一共要安装多少座路灯．
<gadget id="calculator">1_000 / 50</gadget>
<output>20</output>

<gadget id="calculator">2 * 20</gadget>
<output>40</output>

<gadget id="calculator">40 + 1</gadget>
<output>41</output>

<gadget id="calculator">41 * 2</gadget>
<output>82</output>

<result>82</result>