Show the police force shared by counties with location on the east and west.
return counties ;return locations of #1 ;return #1 where #2 is  on the  east ;return #1 where #2 is  on the  west ;return police forces of #3 ;return police forces of #4 ;return police forces in both #5 and #6
['select', 'project', 'comparative', 'comparative', 'project', 'project', 'intersection']