Problem with a cheater
Arrive early and choose a good seat. Focus on the exam and take a bit of care that your work isn't easily visible. Beyond that, relax as much as you can, especially about the circumstances. 

I wouldn't raise any issue with a proctor unless you actually need to, but then, don't hesitate to ask to be reseated. You don't need to offer an explanation unless asked. But you shouldn't have any negative consequences if you need to act. 

Don't do anything that might be interpreted as disruptive such as shouting at someone copying.