The ornamental design for a lamp, as shown and described.
FIG. 1 is a front perspective view of a lamp in accordance with my design;
FIG. 2 is a back perspective view of the lamp in accordance with my design;
FIG. 3 is a front elevation view of the lamp in accordance with my design;
FIG. 4 is a back elevation view of the lamp in accordance with my design;
FIG. 5 is a top plan view of the lamp in accordance with my design;
FIG. 6 is a bottom plan view of the lamp in accordance with my design; and,
FIG. 7 is a side elevation view of the lamp in accordance with my design, the other side being a mirror image thereof.
The broken-line disclosure of elements is understood to represent portions of the article in which the design is embodied, but which form no part of the claimed design.