There are 25 telephone poles on one side of the road, and there is a billboard between every two poles. How many billboards are there in total?
公路的一边有25根电线杆，每两根电线杆之间有个广告牌，一共有多少个广告牌．
<gadget id="calculator">25 - 1</gadget>
<output>24</output>

<gadget id="calculator">1 * 24</gadget>
<output>24</output>

<result>24</result>