Several students are sitting in a circle. Each student has an even
(though not necessarily the same) number of wrapped pieces of candy.
On a signal, each student passes half of his or her trove to the student
on his or her right. Between signals, the teacher (reaching into an
inexhaustible goody bag) gives any student left with an odd number of
candies an extra piece to make the number even before repeating the
maneuver.