  We present the state-of-the art shell model calculations in a large model
space (pf for protons, fpgd for neutrons), which allow to study simultaneously
excitations across the Z=28 and N=50 shell gaps. We explore the region in the
vicinity of 78Ni, being a subject of intense experimental investigations. Our
calculations account correctly for the known low lying excited states in this
region, including those which may correspond to cross-shell excitations. We
observe the minimum of the N=50 mass gap at Z=32 consistent with experimental
data and its further increase towards Z=28, indicating a robustness of the N=50
gap in 78Ni. The evolution of N=50 gap along the nickel chain is shown to bear
similarities with what is know in oxygen and calcium chains, providing a new
opportunity for the studies of 3-body monopole effects in medium mass nuclei.
