Rule TripletLoop
  input '1'
  output '2' or '3'
Flow
  rule TripletA
  rule TripletB
  rule TripletC
End

Rule TripletA
  input '1'
  output '2'.touch
End

Rule TripletB
  input '2'
  output '3'.touch
End

Rule TripletC
  input '3'
  output '1'.touch
End