A tree is planted every 1 meter between two buildings, and a total of 8 trees are planted. How many meters are there between the two buildings?
两幢楼之间每隔1米种一棵树，一共种了8棵树，这两幢楼之间相距多少米？
<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<result>27</result>