Justin Bieber is ready to kick off his Purpose tour next week in Seattle and he wants to make the moment extra special for all his fans. How? By sharing the stage with a few lucky Beliebers.Bieber's team announced a contest that will let four lucky fans, one from each city on his Purpose tour, dance with him onstage. In a video, Nick DeMoura, the creative director and choreographer for Bieber's Purpose tour, explains that contestants have to learn the steps to Bieber's “Children” routine, download the song, and film themselves performing.DeMoura also spends a good deal of the video breaking down the choreography for "Children," step-by-step.Good news: You have until March 7 to submit your video. Bad news: This contest is only for Beliebers who are 18 and under.But who knows? Maybe the Biebs will make a new contest for those grown-up die-hards who've been practicing the moves to "Sorry" for months.You can watch DeMoura's instructional video, below. May the best dancer win!