Task: Question Answering
Input (English): Passage: George Roger Waters (born 6 September 1943) is an English songwriter, singer, bassist, and composer. In 1965, he co-founded the progressive rock band Pink Floyd. Waters initially served solely as the bassist, but following the departure of songwriter Syd Barrett in 1968, he also became their lyricist, co-lead vocalist, and conceptual leader.
Pink Floyd achieved international success with the concept albums The Dark Side of the Moon (1973), Wish You Were Here (1975), Animals (1977), and The Wall (1979). By the early 1980s, they had become one of the most critically acclaimed and commercially successful groups in popular music; by 2013, they had sold more than 250 million albums worldwide. Amid creative differences, Waters left in 1985 and began a legal dispute with the remaining members over the use of the band's name and material. They settled out of court in 1987.
Waters' solo work includes the studio albums The Pros and Cons of Hitch Hiking (1984), Radio K.A.O.S. (1987), Amused to Death (1992), and Is This the Life We Really Want? (2017). In 2005, he released Ça Ira, an opera translated from Étienne and Nadine Roda-Gils' libretto about the French Revolution.
In 1990, Waters staged one of the largest rock concerts in history, The Wall – Live in Berlin, with an attendance of 450,000. As a member of Pink Floyd, he was inducted into the U.S. Rock and Roll Hall of Fame in 1996 and the UK Music Hall of Fame in 2005. Later that year, he reunited with Pink Floyd bandmates Mason, Wright and David Gilmour for the Live 8 global awareness event, the group's first appearance with Waters since 1981. He has toured extensively as a solo act since 1999; he performed The Dark Side of the Moon in its entirety for his world tour of 2006–2008, and in 2010 began the Wall Live tour, the highest-grossing of all time by a solo artist. 
Question: What is the last name of the person who became the co-lead vocalist of Pink Floyd in 1968?
Output (English): Waters.