Hello,
I will be staying for 2 days near RER station "Ivry sur Seine" (zone 2 - at the edge of zone 1 :\ ). What type of ticket should I use to get to the center (zone 1)? And do I have to have two tickets for metro and RER?
Thanks.

P.S. Sorry if this has been answered, I'm kinda in a rush, so no time for proper search.