Russia also officially known as the Russian Federation, is a country in northernEurasia. It is a federal semi-presidential republic, comprising 83 federal subjects. From northwest to southeast, Russia shares borders with Norway, Finland, Estonia, Latvia, Lithuania and Poland (both via Kaliningrad Oblast), Belarus, Ukraine, Georgia, Azerbaijan, Kazakhstan, China, Mongolia, and North Korea. It also has maritime borders with Japan by the Sea of Okhotsk, and the U.S. state of Alaska across theBering Strait. At 17,075,400 square kilometres (6,592,800 sq mi), Russia is the largest country in the world, covering more than one-eighth of the Earth’s inhabited land area. Russia is also the world’s ninth most populous nation with 143 million people as of 2012. Extending across the whole of northern Asia, Russia spans nine time zonesand incorporates a wide range of environments and landforms. Russia has the world’s largest reserves of mineral and energy resources and is the largest producer of oiland natural gas globally. Russia has the world’s largest forest reserves andits lakes contain approximately one-quarter of the world’s fresh water. The nation’s history began with that of the East Slavs, who emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by aVarangian warrior elite and their descendants, the medieval state of Rus arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culturefor the next millennium. Rus’ ultimately disintegrated into a number of smaller states; most of the Rus’ lands were overrun by the Mongol invasion and became tributaries of the nomadic Golden Horde. The Grand Duchy of Moscow gradually reunified the surrounding Russian principalities, achieved independence from the Golden Horde, and came to dominate the cultural and political legacy of Kievan Rus’. By the 18th century, the nation had greatly expanded through conquest, annexation, and exploration to become the Russian Empire, which was the third largest empire in history, stretching from Poland in Europe to Alaska in North America.