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Serie A is a title that Ambrosini won with AC Milan. Serie A is the top division of Italian football, and it is one of the most prestigious leagues in the world. Ambrosini won four Serie A titles with AC Milan, in the 2003-04, 2010-11, 2010-11, and 2011-12 seasons. He was a key player for AC Milan during his time there, and he helped the club to achieve great success.