The ornamental design for a lamp, as shown and described.
FIG. 1 is a front and side perspective view of a lamp showing our new design in a first orientation in which the front panel is in an extended state;
FIG. 2 is a bottom side view thereof in a second orientation;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof;
FIG. 7 is a front view thereof;
FIG. 8 is a rear view thereof; and,
FIG. 9 is a bottom side view thereof in a third orientation in which the front panel is in a depressed state.
The broken lines shown in the Figures of the power receptacle and ground surface, as well as their respective placement, size and configuration, illustrate the environment only and form no part of the claimed design.