 Complete the following phrase:  Mario Andretti is the most successful Formula One driver to drive as an American, but he did not leave his native Italy until the age of 15. He raced in IndyCars from 1964 and, from 1968, spent time commuting to Europe to make appearances in Formula One races. Between his debut with Lotus at the 1968 Italian Grand Prix and the end of the 1974 season Andretti started 21 of the 84 races, driving for four teams. His first race with Ferrari brought about his first win  the 1971 South African Grand Prix. Andretti eventually decided to sign up as a full-time driver with Parnelli in 1975, but after a little over two seasons and no real success the team withdrew from Formula One. He signed with Lotus for the remainder of the season and, by the end of the year, was beginning to achieve some good results including a win at the 1976 Japanese Grand Prix. The car proved fast but unreliable for the following season, and Andrettis four wins took him up to third in the championship. With the problems solved for the following year he was able to win six races and the drivers title. The decisive victory came at the 