How can i ignore a Parameter in SSRS Report

Hi I have an SSRS report that has 3 parameters @City, @County & @Country. When i run the report it wants all the parameters to have a value. I want to be able to just select Cities and ignore the other 2 parameters or  in some cases select a City and Country and ignore County etc.

How can i achieve this without having to create 3 separate reports?

Here is my where clause.

where C.StateCode = 0 AND C.address1_country IN (@Country) AND C.address1_city IN (@City) AND C.address1_county IN (@County) 

All 3 parameters also allow multiple values.