Who was the last college senior (used all four years of college eligibility) to be the first pick in the NBA draft?

Kenyon Martin was drafted first overall in the year 2000, after his senior year of college at the University of Cincinnati. He played all four years, though his first year was not a starting role for the most part (only appearing in 22 games, and starting 3 of them). No first overall pick after him played all four years of college (or even particularly close to it).