Switch Parameter Values correctly.

Hello I am trying to get a certain parameter value to show.

E.g. I have 3 different parameter values, 1 ,2, and 3.   I am trying to create another parameter value which switches and shows me either 1 or 2 or 3.  Depending if there are parameter values inserted into it. 

So I have written this code.  

	   =Switch(Not(IsNothing(Parameters!1.Value)),Parameters!1.Value
               ,IsNothing(Parameters!1.Value),Parameters!2.Value,
			   (IsNothing(Parameters!1.Value) And IsNothing(Parameters!2.Value)), Parameters!3.Value)

This works for showing parameter 1 correctly, 

If parameter 1 is blank/null then parameter 2 shows correctly. 

It fails on Parameter 1 and parameter 2 is blank/null then show parameter 3.  So what am I doing wrong on the 3rd line for it not to show me parameter 3?

Any help would be great.