Is there a bank at the airport with an ATM?
Yes, there's an ATM at the airport - several in fact. Use that rather than the airport exchange offices which give a very bad rate.
A quick tip - debit/credit cards on the Mastercard network tend to give a better rate than ones on the visa network. You might also google your debit card to see if it's particulary praised or criticised for t&c when using abroad.
Another way (perhaps the best) is to bring Euros in cash and exchange them at any kantor (avoid 24 hour ones, hotel ones or ones in the most touristy of areas like Mragowo - just use a normal one, most towns have several) since these always give the best rates.