How to decide one, two or three players in a 20-player game in three hours?

One group 10, and the other group 10, were eliminated by lottery; After the first round of elimination, the remaining five people in the two groups * * * said 10 and then drew lots to eliminate them, and five people were decided after the second round; One of the five people drew lots for a bye, and the other four drew lots for matching and elimination, so after the third round, two people were decided and they entered the semi-finals; Two of the four losers drew 1 and 1 which had just been eliminated by bye, and decided that 1 and 1 which had just not been drawn also entered the semi-finals; The top four draw lots to be eliminated, and the two decide to enter the finals. The two losers compete for 3 or 4 places, and the two finalists compete for 1 and 2 places.