The film "Casablanca" was adapted from what unproduced stage play?

The 1942 film Casablanca was adapted from the unproduced stage play Everybody Comes to Rick’s, written by Murray Burnett and Joan Alison. Warner Bros. purchased the rights to the play before it was ever performed on Broadway, recognizing its strong dramatic potential and timely World War II setting. Although the film was not expected to become a major hit during production, it went on to become one of the most celebrated movies in Hollywood history, winning three Academy Awards, including Best Picture, Best Director, and Best Screenplay.