R -> Rin Rin -> R Rin -> R R -> Rin x1 -> x1p x1p -> x1 x1p -> x1 x1 -> x1p x2 -> x2p x2p -> x2 x2p -> x2 x2 -> x2p x3 -> x3p x3p -> x3 x3p -> x3 x3 -> x3p