  In the present paper we show that the Levy-Ito representation of the
infinitesimal generator $L$ for Levy processes $X_t$ can be written in a
convolution-type form. Using the obtained convolution form we have constructed
the quasi-potential operator $B$. We denote by $p(t,\Delta)$ the probability
that a sample of the process $X_t$ remains inside the domain $\Delta$ for
$0{\leq}\tau{\leq}t$ (ruin problem). With the help of the operator $B$ we find
a new formula for $p(t,\Delta)$. This formula allows us to obtain long time
behavior of $p(t,\Delta)$.
