It's 50/50. See picrel. You can literally simulate this with some very simple code:
https://www.online-python.com/2VS9a71BWAThese probability troll threads are literally older than /pol/. People think that it is hilarious to insist on an incorrect answer like 2/3 and then make people who don't know that it is a troll go insane trying to 'explain'
This is a well known and simple probability problem that anyone can google and have a simple explanation within 2 minutes. Anyone insisting it is 2/3 or 1/3 is definitely trolling.
https://www.online-python.com/2VS9a71BWAhttps://www.online-python.com/2VS9a71BWAhttps://www.online-python.com/2VS9a71BWAi dare you to find a flaw in this code