Passage: Cheryl auditioned for the reality television show Popstars: The Rivals in 2002, which aimed to create a boy band and a girl group to compete for the Christmas number one spot on the UK Singles Chart. She sang "Have You Ever" in her audition, and was one of twenty contestants (ten girls and ten boys) chosen as finalists by judges Pete Waterman, Louis Walsh and Geri Halliwell. The finalists performed live on Saturday evenings, with one gender performing each week, and each week the contestant polling the fewest phone votes was eliminated, until the final line-ups of the five-piece groups emerged. Cheryl was in danger of elimination twice, surviving over Emma Beard and Aimee Kearsley in consecutive performing weeks. On 30 November 2002, she was the first contestant to qualify for the girl group, and was joined by Nadine Coyle, Sarah Harding, Nicola Roberts and Kimberley Walsh to form Girls Aloud, following the final public vote. The group's debut single "Sound of the Underground" peaked at number one on the UK Singles Chart, becoming the 2002 Christmas number one over boy band One True Voice's "Sacred Trust / After You're Gone". Girls Aloud hold the record for the shortest time between being formed as a band and achieving a number one single.Girls Aloud released their debut album Sound of the Underground in May 2003, which entered the charts at number two and was certified platinum by the British Phonographic Industry (BPI) later the same year. Their singles "I'll Stand by You", "Walk This Way", and "The Promise" charted at number one. Two of their albums reached the top of the UK Albums Chart: their greatest hits album The Sound of Girls Aloud and 2008's Out of Control, both of which entered the chart at number one, with over one million copies of the former being sold.

Question: What were the contestants competing for?
the Christmas number one spot on the UK Singles Chart