A couple with three children waited in line at San Francisco's Pier 41 to purchase tickets for a sightseeing boat to Alcatraz Prison.  The children weren't good at waiting: they fidgeted, whined, and punched one another.  The frazzled parents reprimanded them to no avail.

Finally they reached the ticket window.

"Five tickets, please," the father said.  "Two round trip, three one way."