Task: Question Answering
Input (English): Passage: New York City's Central Park, an oasis that functions as the city's "green lung", was in a state of deterioration in the mid-1970s. Though Central Park had been designated a National Historic Landmark in 1962, at the start of the 1980s, the city lacked the financial resources to spend an estimated US$3,000,000 to restore or even to maintain the park. The nonprofit Central Park Conservancy was founded in 1980, and began a successful campaign to raise renovation funds.In the early 1980s, Parks Commissioner Gordon Davis, responsible for New York City's green areas, and Ron Delsener, one of the city's most influential concert promoters, developed the idea of helping Central Park financially with a free open-air concert, under the legal guidance of Bob Donnelly. The city would use profits from merchandising, television, and video rights to renovate the park. Earlier park performances by Elton John and James Taylor showed that this concept could be a success. Davis authorized the project, and Delsener entered discussions with cable TV channel HBO to decide who would perform.They decided on Simon & Garfunkel, a group that had formed in New York City in the 1960s, and had been one of the most successful folk rock groups through the late 60s/early 70s. Simon & Garfunkel had broken up at the height of their popularity and shortly after the release of their fifth studio album, Bridge Over Troubled Water, which is deemed to be their artistic peak and which topped the 1970 Billboard charts for ten weeks. They had grown apart artistically and did not get along well with each other. In the following eleven years, both continued musical careers as solo artists, and worked together only sporadically on single projects. Garfunkel made brief guest appearances at Simon's concerts, which were always successful.Delsener presented the plan to Paul Simon in the summer of 1981. Simon was enthusiastic about the idea, but questioned whether it could be financially successful, especially given the poor audience attendance of his last project, the autobiographical movie One-Trick Pony. Simon's confidence had declined and he had sought treatment for depression. He questioned whether he and Art Garfunkel could work together, but contacted Garfunkel, who was vacationing in Switzerland. Garfunkel was excited about the idea, and immediately returned to the US.From the promoter's viewpoint, Simon and Garfunkel were ideal choices. Not only were they likely to draw a large crowd to the concert, they also had roots in the city –  both had grown up and gone to school in Forest Hills, Queens. Music critic Stephen Holden pointed out that, unlike artists who had left in pursuit of lifestyles offered by other locales, the two had always been a part of New York City. Both gained inspiration from the cityscape and the cultural variety of New York, and spoke of these influences in their songs. 
Question: What are the last names of the two individuals who reportedly did not get along well and had grown apart artistically?
Output (English): Simon.