  We present the generating function for the numbers of isomorphism classes of
coverings of the two-dimensional sphere by the genus $g$ compact oriented
surface not ramified outside of a given set of $m+1$ points in the target,
fixed ramification type over one point, and arbitrary ramification types over
the remaining $m$ points. We present the genus expansion of this generating
function and prove, that the generating function of coverings of genus $0$
satisfies some system of differential equations. We show that this generating
function is a specialization of the function from paper \cite{GJ} and,
therefore, satisfies the KP-hierarchy.
