Obviously running two laps around the school playground is 400 meters, which is exactly 1 kilometer.
明明绕学校操场跑两圈是400米，还差多少正好是1千米．
<gadget id="calculator">1 * 1_000</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 - 400</gadget>
<output>600</output>

<result>600</result>