  In this work we propose a discretization of the second boundary condition for
the Monge-Ampere equation arising in geometric optics and optimal transport.
The discretization we propose is the natural generalization of the popular
Oliker-Prussner method proposed in 1988. For the discretization of the
differential operator, we use a discrete analogue of the subdifferential.
Existence, unicity and stability of the solutions to the discrete problem are
established. Convergence results to the continuous problem are given.
