It is better to take the form of elimination, because 2 1 class is odd, which exists in the case that some classes have a bye in the first round.
Classes with 10 can be selected by drawing lots. The classes with 10 take part in the first round of competition, and the remaining classes with 1 1 are lucky to have a bye in the first round.
After elimination, 10 class produced five advanced teams. These five advanced teams are combined with 1 1 the first round bye team * * * to form 16 teams. We'll arrange it later and eliminate it all.