  We consider the heavy-dense limit of QCD at finite fermion density in the
canonical formulation and approximate it by a 3-state Potts model. In the
strong coupling limit, the model is free of the sign problem. Away from the
strong coupling, the sign problem is solved by employing a cluster algorithm
which allows to average each cluster over the Z(3) sectors. Improved estimators
for physical quantities can be constructed by taking into account the triality
of the clusters, that is, their transformation properties with respect to Z(3)
transformations.
