A total of 28 trees are planted on both sides of an avenue from the beginning to the end, and the distance between every two trees is 8 meters. How long is the avenue in meters?
一条大道的两侧从头到尾共种了28棵树，每两棵树之间相隔8米，这条大道长多少米？
<gadget id="calculator">28 / 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 1</gadget>
<output>13</output>

<gadget id="calculator">13 * 8</gadget>
<output>104</output>

<result>104</result>