function selectUser(nbUser){
let user1= {"songs":FileAttachment("songs_json@5.json").json(),"user_songs":FileAttachment("user_songs_json@3.json").json()},
user2={"songs":FileAttachment("songs_json@6.json").json(),"user_songs":FileAttachment("user_songs_json@4.json").json()};
return [user1,user2][nbUser]
}