There are 30 counties in a certain area, and each county has 3 roads leading to other counties. How many roads are there between these counties?
某地区有30个县城，每个县城都有3条公路通向别的县城，这些县城之间共有多少条公路．
<gadget id="calculator">30 - 1</gadget>
<output>29</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">29 * 3 * 15</gadget>
<output>1_305</output>

<result>1_305</result>