There were 6 balls with identical appearance, except for their integer labels 1 through 6, which initially matched their weights. Some XYSer passed by, randomly swapped the labels as many times as she/he wants, then stole a ball before going away. Now, give Fang a broken balance with 0<imbalance<1, without standard weights, how many trials are needed before it may be determined that the labels are still correct?