The ornamental design for a lamp, as shown and described.
FIG. 1 is a front perspective view of the present invention.
FIG. 2 is a bottom plan view of FIG. 1.
FIG. 3 is a right side elevation view of FIG. 1.
FIG. 4 is a left side elevation view of FIG. 1.
FIG. 5 is a front elevation view of FIG. 1.
FIG. 6 is a rear elevation view of FIG. 1; and,
FIG. 7 is a top plan view of FIG. 1.
The surfaces are lined for contour only and no claim is made to any particular surface texture. The dashed lines indicated disclaimed portions of the design, and no claim is made to the designated portions indicated by dashed lines, including without limitation pivot and support members, support elements, screw or bolt members and recesses, switch-regions and the light element surface itself.