  High-$T_c$ superconductors with CuO$_2$ layers, manganites
La$_{1-x}$Sr$_x$MnO$_3$, and cobaltites LaCoO$_3$ present several mysteries in
their physical properties. Most of them are believed to come from the
strongly-correlated nature of these materials. From the theoretical viewpoint,
there are many hidden rocks in making the consistent description of the band
structure and low-energy physics starting from the Fermi-liquid approach. Here
we discuss the alternative method -- multielectron approach to the electronic
structure calculations for the Mott insulators -- called LDA+GTB (local density
approximation + generalized tight-binding) method. Its origin is a
straightforward generalization of the Hubbard perturbation theory in the atomic
limit and the multiband $p-d$ Hamiltonian with the parameters calculated within
LDA. We briefly discuss the method and focus on its applications to cuprates,
manganites, and cobaltites.
