One lap of the playground runway is 400 meters. After running 2 laps, how many meters are left is 1 kilometer.
操场跑道一圈是400米，跑了2圈后，还差多少米是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>