  Conditions of optimal (synchronized) collisions of any number of solitons and
breathers are studied within the framework of the Gardner equation with
positive cubic nonlinearity, which in the limits of small and large amplitudes
tends to other long-wave models, the classic and the modified Korteweg -- de
Vries equations. The local solution for an isolated soliton or breather within
the Gardner equation is obtained. The wave amplitude in the focal point is
calculated exactly. It exhibits a linear superposition of partial amplitudes of
the solitons and breathers. The crucial role of the choice of proper soliton
polarities and breather phases on the cumulative wave amplitude in the focal
point is demonstrated. Solitons are most synchronized when they have
alternating polarities. The straightforward link to the problem of
synchronization of envelope solitons and breathers in the focusing nonlinear
Schr\"odinger equation is discussed (then breathers correspond to envelope
solitons propagating above a condensate).
