  We derive a new Banks-Casher-type relation which relates the density of
complex Dirac eigenvalues at the origin to the BCS gap of quarks at high
density. Our relation is applicable to QCD and QCD-like theories without a sign
problem, such as two-color QCD and adjoint QCD with baryon chemical potential,
and QCD with isospin chemical potential. It provides us with a method to
measure the BCS gap through the Dirac spectrum on the lattice.
