Before revision:  For any L\'{e}vy process X satisfying a Cram\'{e the solution of this problem , which is given in terms of a quasi-invariant distribution of the process X killed at the epoch of first entrance into the negative half-axis.
After revision:  For any L\'{e}vy process X satisfying a Cram\'{e the solution of this problem in terms of a quasi-invariant distribution of the process X killed at the epoch of first entrance into the negative half-axis.