The chief executive officer of a city shall be a mayor. The chief executive officer of a village shall be a village president, who may also be called a mayor. The chief executive officer of an incorporated town shall be a president, who may also be called a mayor. The chief executive officer shall hold office for 4 years and until a successor is elected and has qualified, except in municipalities that have adopted a 2 year term as provided in Section 3.1-10-65 and except in a village or incorporated town that, before January 1, 1942, has adopted a 2 year term for the chief executive officer.