America is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the west across the Bering Strait. At 3.79 million square miles (9.83 million square km) and with about 306 million people, the United States is the third or fourth largest country by total area, and third largest by land area and by population. The National flowers of the USA is the Rose. The most popular flowers favored by the Americans include Carnations, Roses, Orchids, Gerberas and exotic varieties.