  The Friedman--Mineyev theorem, earlier known as the (strengthened) Hanna
Neumann conjecture, gives a sharp estimate for the rank of the intersection of
two subgroups in a free group. We obtain an analogue of this inequality for any
two subgroups in a virtually free group (or, more generally, in a group
containing a free product of left-orderable groups as a finite-index subgroup).
