The principle of drawing lots is based on:
1, the first place in the small group is against the second place in other groups, which is the principle of avoidance between teams in the same group.
2. Avoid teams in the same league, that is, two Premier League teams or two La Liga teams can't meet in the final of 1/8 in advance.
The principle of 16 is that the second place in the group is the first place, and the first place in the group is the first place.