If 100 trees are planted on both sides of a road, exactly every 3 meters, and the same number of trees are planted on both sides, how long is the road?
在一条马路两旁种100棵树，正好每隔3米一棵，而且两边种的树同样多，这条马路长多少米？
<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<gadget id="calculator">50 - 1</gadget>
<output>49</output>

<gadget id="calculator">49 * 3</gadget>
<output>147</output>

<result>147</result>