A wire is 1 km long and 810 meters have been used up. How many meters are left on the wire?
一根电线长1千米，用去了810米，这根电线还剩多少米？
<gadget id="calculator">1 * 1_000</gadget>
<output>1_000</output>

<gadget id="calculator">1_000 - 810</gadget>
<output>190</output>

<result>190</result>