  The supercritical instability in a system of two identical charged impurities
in gapped graphene described in the continuous limit by the two-dimensional
Dirac equation has been studied. The case where the charge of each impurity is
subcritical, but their sum exceeds the critical value calculated in the version
with a single Coulomb center, is considered. Using the developed variational
method, the dependence of the critical distance $R_{\rm cr}$ between the
impurities on their total charge is calculated. The $R_{\rm cr}$-value is found
to grow as the total impurity charge increases and the quasiparticle band gap
decreases. The results of calculations are compared with those obtained in
earlier researches.
