The ornamental design for a lamp, as shown and described.
FIG. 1 is a front, top, and right-side perspective view of a lamp, according to an embodiment of the present invention shown;
FIG. 2 is a front elevational view of the lamp shown in FIG. 1;
FIG. 3 is a rear elevational view of the lamp shown in FIG. 1;
FIG. 4 is a right elevational view of the lamp shown in FIG. 1;
FIG. 5 is a left elevational view of the lamp shown in FIG. 1;
FIG. 6 is a top plan view of the lamp shown in FIG. 1; and,
FIG. 7 is a bottom plan view of the lamp shown in FIG. 1.
The broken lines shown in the drawings are shown for illustrative purposes only and form no part of the claimed design. The surface shading, if any, illustrated in the drawings is provided merely to highlight the contour of the design; it is not intended to be illustrative of texture or gloss.