Romania is a country located at the crossroads of Central and Southeastern Europe. It has a coastline on the Black Sea and borders Bulgaria, Hungary, Moldova, Serbia, and Ukraine. Romania has mountain ranges running from the north and west in the interior, which are collectively known as the Carpathians. The government system is a republic; the chief of state is the president, and the head of government is the prime minister. Romania has a mixed economy which includes a variety of private freedom, combined with centralized economic planning and government regulation. Romania is a member of the European Union (EU).