  The Lagrangian (action) formulation of the Chalker-Coddington network model
for plateau-plateau transitions in quantum Hall effect is presented based on a
model of fermions hopping on Manhattan Lattice ($ML$). The dimensionless
Landauer resistance is considered and its average is calculated over the random
U(1) phases with constant distribution on the circle. The Lagrangian of the
resultant model on $ML$ is found and the corresponding $R$-matrix is written
down. It appeared, that this model is integrable, rising hope to investigate
physics of plateau- plateau transitions by the exact method of powerful
Algebraic Bethe Ansatz $(ABA)$.
