  We consider charge quantization in a small superconducting grain that is
contacted by a normal-metal electrode and is controlled by a capacitively
coupled gate. At zero temperature and zero conductance $G$ between the grain
and the electrode, the charge $Q$ as a function of the gate voltage $V_g$
changes in steps. The step height is $e$ if $\Delta<E_c$, where $\Delta$ and
$E_c$ are, respectively, the superconducting gap and the charging energy of the
grain. Quantum charge fluctuations at finite conductance remove the
discontinuity in the dependence of $Q$ on $V_g$ and lead to a finite step width
$\propto G^2\Delta$. The resulting shape of the Coulomb blockade staircase is
of a novel type. The grain charge is a continuous function of $V_g$ while the
differential capacitance, $dQ/dV_g$, has discontinuities at certain values of
the gate voltage. We determine analytically the shape of the Coulomb blockade
staircase also at non-zero temperatures.
