A train of mild SS'ness:

Shopper A and Shopper B finish checking out and exit the checkouts. Shopper A is two checkouts closer to the exit than B, so she reaches the exit just ahead of B. They go into the vestibule like a little choochoo train. There are 2 exterior doors, with the one on the left marked EXIT and the one on the right ENTRANCE. A couple, C, approach the store from the outside, and approach the EXIT door, since it is closer, and pause to enter. A pushes her cart out the door, B pushes her cart to the doorway. A then comes to a complete halt, and starts digging in her purse for her sunglasses. B cannot go forward, because of A; she cannot turn left because of C, and because A's cart is angled to the right, she doesn't try to get around her on the right. A continues to dig. The couple glares, but since A has her back to them, they glare at B.