The grain store originally had 900 kilograms of flour, 500 kilograms were shipped out, and 400 kilograms were brought in. How many kilograms of flour are there in the grain store now?
粮店原来有900千克面粉，运走500千克，又运进400千克，现在粮店有多少千克面粉？
<gadget id="calculator">900 - 500</gadget>
<output>400</output>

<gadget id="calculator">400 + 400</gadget>
<output>800</output>

<result>800</result>