Show the police force shared by counties with location on the east and west.
SELECT Police_force FROM county_public_safety WHERE LOCATION  =  "East" INTERSECT SELECT Police_force FROM county_public_safety WHERE LOCATION  =  "West"
SELECT Police_force FROM county_public_safety WHERE LOCATION  =  "East" INTERSECT SELECT Police_force FROM county_public_safety WHERE LOCATION  =  "West"
[{'Police_force': 'RCMP'}]