15 football team, how to make cups in groups?

Divide into four groups, three groups and four teams, and one group and three teams. No matter how many teams there are in this group, they are the top two. (that is, there are three teams, each team only plays two games, and the teams of other groups play three games. It doesn't matter, as long as the top two teams finish the group stage. ) this is in the top eight.

Then with the method of a1-b2a2-b1c1-d2c2-d1,it is also possible for the four teams to draw lots for the first time to decide which group's second one will become their opponent (in this case, the second one in the same group will not be able to play the game of 8-in-4) and divide it into two halves at the same time.

Then the semi-finals, the 3 rd and 4 th finalists, and the finals.