Jmeter How to make 2 thread group run parallel but not sharing parameter value between thread?

I have a situation like this:

Test Plan
   Thread Group 1
      var A = 1 ( User parameters)
      HTTP request 1
      HTTP request 2 

   Thread Group 2
      var A = 2 ( User parameters)
      HTTP request 3
      HTTP request 4

I know that I can use "Run Thread Groups consecutively" to make these 2 thread run parallel. However, the problem is, because they are running parallel, sometimes var A=2 got recognized in Thread Group 1, and thus make the test case fail. What I ask, is there any way that I can still run these threads parallel and still make sure that the parameter values of these threads won't affect on each other? Thank you!