  I propose a generalization of the Liouville action which corresponds to the
Nambu-Goto string like the usual Liouville action corresponds to the Polyakov
string. The two differ by higher-derivative terms which are negligible
classically but revive quantumly. An equivalence with the four-derivative
action suggests that the Nambu-Goto string in four dimensions can be described
by the (4,3) minimal model analogouslyly to the critical Ising model on a
dynamical lattice. While critical indices are the same as in the usual
Liouville theory, the domain of applicability becomes broader.
