premise: The Africa Cup of Nations had its schedule changed.
hypothesis: Africa Cup of Nations . South Africa was originally scheduled to compete , but were disqualified due to the apartheid policies of the government then in power . The number of participants in the final tournament reached 16 in 1998 ( 16 teams were to compete in 1996 but Nigeria withdrew , reducing the field to 15 , and the same happened with Togo 's withdrawal in 2010 ) , and since then , the format has been unchanged , with the sixteen teams being drawn into four groups of four teams each , with the top two teams of each group advancing to a `` knock-out '' stage .