1996 ACM MID-CENTRAL REGIONAL PROGRAMMING CONTEST
PROBLEM #7 - 18-WHEELER CARAVANS (AKA SEMIGROUPS)

JUDGE'S NOTES

Note that there could be more than one possible reason that a set does
not form a semigroup (test case #4 in the official judge's input data
is an example of such a set).  The problem asks only for one reason,
however, so any valid reason should be judged correct.  For this
reason this problem should not be judged using a text comparison
utility, but rather by visual inspection.

Ron Pacheco
Regional Chief Judge
