Brunei is a country located in Southeast Asia on the island of Borneo. Aside from the South China Sea coastline, it is surrounded by Malaysia. The coastal position puts Brunei close to vital sea lanes linking the Indian and Pacific Oceans. Brunei is mostly flat with mountains in the east. The government is a constitutional sultanate; the chief of state and head of government is the sultan and prime minister. Brunei has a mixed economic system which includes a variety of private freedom, combined with centralized economic planning and government regulation. Brunei is a member of the Asia-Pacific Economic Cooperation (APEC), the Association of Southeast Asian Nations (ASEAN), and the Trans-Pacific Partnership (TPP).