  We propose a gathering protocol for an even number of robots in a ring-shaped
network that allows symmetric but not periodic configurations as initial
configurations, yet uses only local weak multiplicity detection. Robots are
assumed to be anonymous and oblivious, and the execution model is the non-
atomic CORDA model with asynchronous fair scheduling. In our scheme, the number
of robots k must be greater than 8, the number of nodes n on a network must be
odd and greater than k+3. The running time of our protocol is O(n2)
asynchronous rounds.
