The Apartment

1960 film by Billy Wilder

The Apartment is a 1960 American romantic comedy film directed and produced by Billy Wilder from a screenplay he co-wrote with I. A. L. Diamond. Jack Lemmon stars as an insurance clerk who, in hopes of climbing the corporate ladder, allows his superiors to use his Upper West Side apartment to conduct their extramarital affairs. He becomes attracted to an elevator operator (Shirley MacLaine) in his office building, unaware that she is having an affair with the head of personnel (Fred MacMurray).

From Wikipedia, under CC BY-SA. More on occurri.