Estonia adopted a new post-Soviet constitution on 28 June 1992. It declares Estonia a parliamentary democracy with a unicameral parliament. The parliament is known as the Riigikogu, and has 101 seats. Members of parliament serve four-year terms. The president (who is elected for a five-year term), prime minister and the cabinet make up the executive branch of government. The president is the head of state while the prime minister is the head of government. Both the parliament and the president are elected by direct universal suffrage of citizens 18 years or older.