Marino are elected every six months by the Sammarinese parliament, the Grand and General Council. They serve as heads of state and government and are normally chosen from opposing parties. Israel After the 2019-2021 political crisis, the Basic Law of Israel's government underwent a major change. A system of two prime ministers, that can be appointed at the same time by the Knesset, was established. According to the new method, there is an “alternate prime minister” in addition to the main and declared one. After half of the government's term, the two prime ministers change positions and status. However, during the term, the government's roles and duties are divided between the two prime ministers and each one of them is entitled to remove ministers without the other's interference. Historical diarchies Sparta The office of king in ancient Sparta was divided between two kings from separate dynasties, each holding a veto over the other's actions. However, the Spartan kings' powers and duties consisted mainly of leading the Spartan army on campaign (during which only one king would usually lead a given force) and certain religious functions, as well as having ex-officio seats in the Gerousia (Senate). Actual day-to-day public administration in Sparta was managed by the ephors. Roman Republic Following the overthrow of the Roman monarchy, the Romans established an oligarchic Roman Republic which divided supreme executive power () between two consuls, both elected each year and each holding a veto over the other's actions. The historical duumviri were not rulers but magistrates, performing various judicial, religious, or public functions. Hungary The Hungarians originally possessed a system of dual kingship, with religious authority vested in the kende and military authority vested in the war-chief (). It is believed that when the kende Kurszán was killed a little after the arrival of the Hungarians in Pannonia, his role was usurped by the war-chief Árpád, establishing the Hungarian monarchy. It is not known with certainty whether Árpád was originally the kende or the gyula. Medieval Europe A paréage was a feudal treaty recognizing the "equal footing" () of two sovereigns over a territory. The most famous such arrangement was the 1278 treaty that established modern Andorra. Others include Maastricht, which was shared by the Duke of Brabant and the Prince-Bishopric of Liège. After the establishment of the Dutch Republic, it became a condominium of Liège and the United Provinces, which administered it through