Question: what job in film did both Hampton Del Ruth and Frank Pierson share?

Context paragraphs:
Hampton Del Ruth: Hampton Del Ruth (September 7, 1879 – May 15, 1958) was an American film actor, director, screenwriter, and film producer.  Among other work, he wrote the intertitles for the final American studio-made silent film "" (1935).

The Alligator People: The Alligator People is a 1959 CinemaScope science fiction horror film directed by Roy Del Ruth.  It stars Beverly Garland, Bruce Bennett and Lon Chaney Jr. This film was the penultimate feature directed by Del Ruth and quite different than those of his days at Warner Bros.

Girl Crazy (1929 film): Girl Crazy was a 1929 comedy film directed by Mack Sennett and starring Andy Clyde as "a girl-crazy sexagenarian".  The film's story is credited to Hampton Del Ruth, Alfred J. Goulding, Harry McCoy, Earle Rodney, and Mack Sennett.

Frank Pierson: Frank Romer Pierson (May 12, 1925 – July 22, 2012) was an American screenwriter and film director.

In Country: In Country is a 1989 American drama film produced and directed by Norman Jewison, starring Bruce Willis and Emily Lloyd.  The screenplay by Frank Pierson and Cynthia Cidre was based on the novel by Bobbie Ann Mason.  The original music score was composed by James Horner.  Willis earned a best supporting actor Golden Globe nomination for his role.

The Anderson Tapes: The Anderson Tapes is a Technicolor 1971 American crime film in Panavision directed by Sidney Lumet, starring Sean Connery and featuring Dyan Cannon, Martin Balsam, and comedian Alan King.  The screenplay was written by Frank Pierson, based upon a best-selling 1970 novel of the same name by Lawrence Sanders.  The film is scored by Quincy Jones and marks the feature film debut of Christopher Walken.

Dog Day Afternoon: Dog Day Afternoon is a 1975 American crime drama film directed by Sidney Lumet, written by Frank Pierson, and produced by Martin Bregman and Martin Elfand.  The film stars Al Pacino, John Cazale, Charles Durning, Chris Sarandon, Penelope Allen, James Broderick, Lance Henriksen, and Carol Kane.  The title refers to the sultry "dog days" of summer.

Somebody Has to Shoot the Picture: Somebody Has to Shoot the Picture is a 1990 American made-for-television prison drama film written by photojournalist Doug Magee, inspired by his interviews with and photos of death row prisoners.  The film was directed by Frank Pierson.

Why Must I Die?: Why Must I Die?  is a 1960 neo noir film directed by Roy Del Ruth, and starring Terry Moore and Debra Paget.  It was released by American International Pictures as a double feature with "The Jailbreakers".  This was director Roy Del Ruth's final film.

Citizen Cohn: Citizen Cohn is a 1992 cable film covering the life of Joseph McCarthy's controversial chief counsel Roy Cohn.  James Woods, who starred as Cohn, was nominated for both an Emmy and a Golden Globe for his performance.  "Citizen Cohn" also stars Joe Don Baker (as McCarthy), Ed Flanders (as Cohn's courtroom nemesis Joseph Welch), Frederic Forrest (as writer Dashiell Hammett), and Pat Hingle (as Cohn's onetime mentor J. Edgar Hoover).  It was directed by Frank Pierson.  The movie was filmed on location in Pittsburgh, Pennsylvania.

Supporting paragraphs: Hampton Del Ruth Frank Pierson
Answer: American screenwriter and film director