  We describe data on elastic $pp$ scattering at ISR and LHC energies using the
analytical representation of the amplitude as the sum of three exponentials
equipped with complex phases. In addition, we take into account the Coulomb and
Coulomb-nuclear contributions in the entire transfer region and strong
"perturbative" contributions in the large transfer region. Refined values of
basic scattering characteristics are obtained. Significant changes in the
behavior of the amplitude are detected at the transition from ISR to LHC
energies. The results obtained indicate a two-layer structure of the colliding
protons. In the transition to 13 TeV, a sharp increase in the size of the inner
layer and its activity in the scattering is observed. A possible interpretation
of this effect is discussed.
