One lap of the runway of the sports field is 400 meters. Youyou ran 2 laps, and the number of meters you ran was 1 kilometer.
运动场的跑道一圈是400米，优优跑了2圈，再跑多少米就是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>