The second type: grouping system, that is, seven teams are divided into two groups, a group of three and a group of four, with the top two in each group being the top four, and then cross-eliminated.
The third type: single elimination system, in which seven teams draw lots to decide the opponents in the first round, but one team is bye-bye (so the draw must be absolutely fair). After the first round, three teams were eliminated, leaving four teams, and then these four teams were eliminated in a single game. As for the last four knockout matches, it's best to decide when drawing lots. Or draw lots after the first round.