The ornamental design for a lamp, as shown and described.
FIG. 1 is a front elevational view of a first embodiment of a lamp showing
our new design, the rear view being a mirror image and, therefore, not
shown thereof;
FIGS. 2 and 3 are two opposite side views thereof;
FIGS. 4 and 5 are top and bottom plan views respectively thereof; and,
FIG. 6 is a bottom plan view thereof on line 6-6 in FIG. 1.