Three!
The one that took my order did not know how to punch the bread into her checkout machine, so she called the second one to help. Then both of them took about seven confirmations that I, indeed, want the whole loaf, not a half of it. This particular bread comes in large loaves and is priced by halves - the sticker reads "3.98 per 1/2 loaf." The first cashier also did not know how to operate the slicer, so she called yet another one to help with that. At each pause for the next discussion of my order, cashiers checked out somebody else from the line of about ten people that accumulated meanwhile, and I just waited. The third cashier tried, for a while, to cut the bread in half with a tiny knife, failed since it was pretty thick-crusted, and stuck the whole thing into the slicer machine. Apparently, the machine did not work properly as well, or else the whole loaf jammed it. So the third cashier had to stick her hand deep inside the machine to keep pushing the bread toward the knives, while the machine was operating. I could not watch, so I turned away, half-expecting to hear her screams when her hand reached those vibrating knives. Luckily, she managed to slice and pack the bread without injuring herself. Meanwhile, the first cashier charged me for bread - but only for half the loaf. I felt that if I pointed it out to her, she would probably have to call for help again and delay me even more, so I remained silent.
So, I did "earn" four dollars in mistakenly free bread in those ten or so minutes it took three bakery cashiers to sell me one loaf of sliced bread. Still, the whole thing was rather funny.