For xy to be 0, where x and y are the first and second coordinates of a point in the coordinate axes,
either x, or y or both must be 0.
So we consider the points of the form (x, 0), (0, y) and (0, 0). These are the x and y intercepts.
A circle can touch the axes at 1, 2, 3 or 4 points but not more.
Check the picture for examples of all the cases.
Answer: n∈{1, 2, 3, 4}
