The islands are located about halfway between Hawaii and Australia, north of Nauru and Kiribati, east of the Federated States of Micronesia, and south of the U.S. territory of Wake Island, to which it lays claim. The atolls and islands form two groups: the Ratak (sunrise) and the Ralik (sunset). The two island chains lie approximately parallel to one another, running northwest to southeast, comprising about 750,000 square miles (1,900,000 km2) of ocean but only about 70 square miles (180 km2) of land mass. Each includes 15 to 18 islands and atolls. The country consists of a total of 29 atolls and five isolated islands.