One lap of the school playground is 400 meters, and Xiao Ming runs two laps, which is exactly 1 kilometer.
学校操场一圈是400米，小明跑两圈，还差多少，正好是1千米．
<gadget id="calculator">1 * 1_000</gadget>
<output>1_000</output>

<gadget id="calculator">400 * 2</gadget>
<output>800</output>

<gadget id="calculator">1_000 - 800</gadget>
<output>200</output>

<result>200</result>