There are 64 telephone poles on both sides of a bridge, and there is a billboard between every two poles. How many billboards are there in total?
一座大桥的两边共有64根电线杆，每两根电线杆之间有一个广告牌，一共有多少个广告牌？
<gadget id="calculator">64 / 2</gadget>
<output>32</output>

<gadget id="calculator">1 * 32</gadget>
<output>32</output>

<gadget id="calculator">32 - 1</gadget>
<output>31</output>

<result>31</result>