On the side of the road, a tree is planted every 7 meters from the beginning to the end, and a total of 20 trees are planted. How long is the road?
在马路一侧，从头到尾每隔7米种一棵树，一共种了20棵树，这条马路有多长？
<gadget id="calculator">20 - 1</gadget>
<output>19</output>

<gadget id="calculator">19 * 7</gadget>
<output>133</output>

<result>133</result>