i am going to the apple store on the 19th to buy the iphone 6. the store opens at 8am. how early should i get there to make sure 100% that i get a iphone 6

At least,the morning before,if not sooner.

i am going to the apple store on the 19th to buy the iphone 6. the store opens at 8am. how early should i get there to make sure 100% that i get a iphone 6