Example of shock wave in unstaible medium: The focusing nonlinear   Schrodinger equation
  Dissipationless shock waves in modulational unstable one-dimensional medium are investigated on the simplest example of integrable focusing nonlinear Schr\''odinger (NS) equation. Our approach is based on the construction of special exact solution of the Whitham-NS system, which ''partially saturates'' the modulational instability. 
Ramil' F.Bikbaev, Vadim R.Kudashev (Institute of Mathematics,   Chernyshevskii 112, Ufa, Russia)