Brazil is the largest country in South America bounded by the Atlantic Ocean. Neighboring countries include Argentina, Bolivia, Colombia, French Guiana, Guyana, Paraguay, Peru, Suriname, Uruguay, and Venezuela. A geographically large country, the terrain includes lowlands, hills, and some mountains. The Amazon River runs through northeastern Brazil, and the Amazon Rainforest covers about one-third of the country. The government system is a federal republic; the chief of state and head of government is the president. The economic system is a market economy in which the prices of goods and services are determined in a free price system. Brazil is a member of the Common Market of the South (Mercosur).