In test #15 there are radiobeacons which don't have correct location on the plane (i.e. no one of points 1 <= x,y <= 200 is acceptable) but their signals are identified by checkpoints. In the problem statement we can find, that "N radiobeacons are located on the plane" and "we know ... that their coordinates are integers from 1 to 200". So, I believe that such test cases are incorrect.

Yes, my assert also falls.