Consensus number of memory-to-memory swap

Question

I think that consensus number of mem-to-mem-swap(a,b) operation which atomically swaps the values between shared locations a and b (shared R/W memory) is infinite , but I'm having trouble proving it.
I thought about implementing CAS with mem-to-mem-swap but comparing atomically is problematic, I think there is straightforward consensus protocol but I can't think about one.