The ornamental design for a lamp, as shown and described.
FIG. 1 is a top perspective view showing our new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof;
FIG. 9 is a top perspective view of a second embodiment of the new design;
FIG. 10 is a bottom perspective view thereof;
FIG. 11 is a front elevational view thereof;
FIG. 12 is a rear elevational view thereof;
FIG. 13 is a left side elevational view thereof;
FIG. 14 is a right side elevational view thereof;
FIG. 15 is a top plan view thereof; and,
FIG. 16 is a bottom plan view thereof.
The break lines in FIGS. 1-6 and 9-14 are to indicate that the appearance of any portion of the lamp between the break lines forms no part of the claimed design, and the broken line disclosure of portions of the lamp also form no part of the claimed design.