Task: Question Answering
Input (English): Passage: In January 1980, Michael Stipe met Peter Buck in Wuxtry Records, the Athens record store where Buck worked. The pair discovered that they shared similar tastes in music, particularly in punk rock and protopunk artists like Patti Smith, Television, and the Velvet Underground. Stipe said, "It turns out that I was buying all the records that [Buck] was saving for himself." Through mutual friend Kathleen O'Brien, Stipe and Buck then met fellow University of Georgia students Mike Mills and Bill Berry, who had played music together since high school and lived together in Georgia. The quartet agreed to collaborate on several songs; Stipe later commented that "there was never any grand plan behind any of it". Their still-unnamed band spent a few months rehearsing in a deconsecrated Episcopal church in Athens, and played its first show on April 5, 1980, supporting The Side Effects at O'Brien's birthday party held in the same church, performing a mix of originals and 1960s and 1970s covers. After considering Twisted Kites, Cans of Piss, and Negro Eyes, the band settled on "R.E.M." (which is an acronym for rapid eye movement, the dream stage of sleep), which Stipe selected at random from a dictionary.The band members eventually dropped out of school to focus on their developing group. They found a manager in Jefferson Holt, a record store clerk who was so impressed by an R.E.M. performance in his hometown of Chapel Hill, North Carolina, that he moved to Athens. R.E.M.'s success was almost immediate in Athens and surrounding areas; the band drew progressively larger crowds for shows, which caused some resentment in the Athens music scene. Over the next year and a half, R.E.M. toured throughout the Southern United States. Touring was arduous because a touring circuit for alternative rock bands did not then exist. The group toured in an old blue van driven by Holt, and lived on a food allowance of $2 each per day.During April 1981, R.E.M. recorded its first single, "Radio Free Europe", at producer Mitch Easter's Drive-In Studios in Winston-Salem, North Carolina. Initially distributing it as a four-track demo tape to clubs, record labels and magazines, the single was released in July 1981 on the local independent record label Hib-Tone with an initial pressing of 1,000 copies—600 of which were sent out as promotional copies. The single quickly sold out, and another 6,000 copies were pressed due to popular demand, despite the original pressing leaving off the record label's contact details. Despite its limited pressing, the single garnered critical acclaim, and was listed as one of the ten best singles of the year by The New York Times. 
Question: What are the full names of the four individuals in the quartet that agreed to collaborate on several songs?
Output (English): Mike Mills.