Yeping has newly built a 5km long and 60m wide Soviet Avenue. Workers are installing street lights on both sides of the road every 20 meters (at both ends). How many street lights need to be installed in total?
叶坪新修了一条长5千米，宽60米的苏维埃大道，工人师傅正在道路两旁每隔20米安装路灯(两端要装)，一共需要安装多少盏路灯．
<gadget id="calculator">1_000 / 20</gadget>
<output>50</output>

<gadget id="calculator">5 * 50</gadget>
<output>250</output>

<gadget id="calculator">250 + 1</gadget>
<output>251</output>

<gadget id="calculator">251 * 2</gadget>
<output>502</output>

<result>502</result>