On one side of a road with a length of 1 km, set up telephone poles at intervals of 50 meters. If there are no poles at both ends of the road, how many poles are needed in total?
在一条长1千米的公路一侧架设电线杆，每隔50米架设一根，若公路两端不架，共需电线杆多少根？
<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>19</output>

<result>19</result>