Szczecin is not being considered on a coast, but on river Oder. Also, technically Copenhagen is not on the cost of the Baltic sea - Baltic border is between Falsterbo in Sweden and Stevns Lighthouse in Denmark, which is below Copenhagen.
I've made some changes to this quiz. Read the instructions if you face any problems. As the city of Szczecin isn't on the actual coast of Poland, I deleted it. Please comment if any other mistakes.