March Madness includes 4 "play-in" games where 8 teams compete for the last four spots in the 64-team bracket. These games take place on the 2 days before the rest of the tournament kicks off. When completing brackets, you are not typically expected to pick the outcome of these "play-in" games, but rather you can fill out a bracket all the way until the "Round of 64" begins (and the results of the "play-in" games are known).

Therefore this website allows you to pick the results for each scenario that could occur in the play-in games. Once you know the result of the play-in games, you can update your bracket according to those results and you should have only one team per every line in the bracket.