Plant trees on one side of the road from the beginning to the end, planting one tree every 9 meters, planting a total of 100 trees, how long is this road?
在路的一侧从头至尾栽树，每隔9米栽一棵，共栽了100棵，这条路有多长？
<gadget id="calculator">100 - 1</gadget>
<output>99</output>

<gadget id="calculator">99 * 9</gadget>
<output>891</output>

<result>891</result>