Bolivia is a landlocked country in South America that borders the countries of Argentina, Brazil, Chile, Paraguay, and Peru. Bolivia is located in the rugged Andes Mountain with highland plateau and lowland plains of the Amazon basin. Bolivia shares control of Lago Titicaca, the world's highest navigable lake. The government system is a republic; the new constitution defines Bolivia as a "Social Unitarian State." The chief of state and head of government is the president. Bolivia has a mixed economic system which includes a variety of private freedom, combined with centralized economic planning and government regulation. Bolivia is a member of the Andean Community (ANCOM).