What is the plot of John Updike's short story "A&P"?

John Updike's short story, "A&P," is a
slice-of-life tale about Sammy, the protagonist-narrator and teenage cashier in a New
England grocery store. One day at work, three teenage girls come into the store clad
only in bathing suits. Sammy becomes so distracted that he can't remember if he has rung
up his last customer's goods. The three girls--described by Sammy as "a chunky one... a
tall one" with a long chin, and the "queen"--continue their shopping while he and a
co-worker gossip about the three underdressed girls. When the girls arrive at Sammy's
checkout counter, "Queenie" produces a dollar bill from her bathing suit top, causing
Sammy more lustful distress. However, the store manager chastizes the girls for their
scantily-clad dress, which embarrasses the girls. As they leave, Sammy, in an act which
he considers chivalrous (but which goes unnoticed by the girls), tells the manager that
he quits. The manager, a friend of Sammy's parents, tries to convince him to remain, but
Sammy rings up a "no sale" on the register, and storms out of the store. Without a job
and likely to draw the ire of his angry parents, Sammy's summer --and his immediate
future--appears to be threatened by his abrupt decision.