During the first half of January 2023, everyone who works with cash in the Republic of Croatia must receive both euros and Croatian kuna, and return the rest exclusively in euros. This application makes it easy to calculate how much money has been received in total and how much needs to be returned or how much is missing in relation to the amount of the bill. In addition, it also contains a classic currency converter between these two currencies. The application was developed at the STEM workshops of the Pazin Radio Club with a donation from DPD Croatia doo, for which we thank them.