Ordinary elimination system is the best.
50 people are divided into 25 groups, and lots are drawn to decide who is in this group.
Two people in each group, play a game, decide the outcome, the winner will advance and the loser will be eliminated.
There are 25 people left.
Divide into 12 groups, with 2 people in each group, leaving 1 person. This person will go straight to the next round or draw lots.
There are 13 people left in the third round. Keep drawing lots. There are 1 person left in Group 6, and1* * 7 people will enter the next round.
In the fourth round, a ***7 people, for the same reason, drew lots, had a bye, and were eliminated, leaving 3 people.
The fifth round, a ***3 people, these three people want to make a round robin 123.
I hope this helps.