A bottle of beverage is 4 liters in total, and 21 cups have been poured in a plastic cup with a capacity of 180 ml. How many milliliters are left in the beverage bottle?
一瓶饮料共4升，用容量180毫升的塑料杯连倒了21杯，饮料瓶中还剩下多少毫升？
<gadget id="calculator">4 * 1_000</gadget>
<output>4_000</output>

<gadget id="calculator">180 * 21</gadget>
<output>3_780</output>

<gadget id="calculator">4_000 - 3_780</gadget>
<output>220</output>

<result>220</result>