  The purpose of this note is to provide a transparent and unified retelling of
both Skvortsov's proof of the structural completeness of Medvedev's logic of
finite problems, which is a classical result originally due to Prucnal, and of
Levin's proof that Medvedev's logic of finite problems is the largest extension
of the (weak) Kreisel-Putnam logic with the disjunction property. Presenting
both results together allows us to simplify their presentation, as they both
hinge on the same lemma. There is no novel content in this note, its purpose is
merely to present the material in a more accessible way.
