Bulgaria is located in Southern Europe, situated on the eastern Balkan Peninsula. It is a mostly mountainous country surrounded by Greece, Macedonia, Romania, Serbia, and the Black Sea. Bulgaria has strategic access to the Turkish Straits and controls key land routes to Europe and to the Middle East. The government system is a parliamentary republic; the chief of state is the president, and the head of government is the prime minister. Bulgaria has transitioned to a market economic system in which the prices of goods and services are determined in a free price system. Bulgaria is a member of the European Union (EU).