A collective head of state can exist in republics (internal complexity), e.g., nominal triumvirates, the Directoire, the seven-member Swiss Federal Council (where each member acts in turn as president for one year), Bosnia and Herzegovina with a three-member presidency from three nations, San Marino with two "captains-regent" which maintains the tradition of Italian medieval republics that had always had an even number of consuls. A diarchy, in two rulers was the constitutional norm, may be distinguished from a coregency, in which a monarchy experiences an exceptional period of multiple rulers.