The supermarket shipped back a batch of stationery, sold 145 pieces on the first day, and left 257 pieces. How many pieces of stationery did the supermarket ship back?
超市运回一批文具，第一天卖出145件，剩下257件，超市运回文具多少件？
<gadget id="calculator">145 + 257</gadget>
<output>402</output>

<result>402</result>