The ornamental design for a lamp, as shown and described.
The file of this patent contains at least one drawing/photograph executed in color. Copies of this patent with color drawing(s)/photograph(s) will be provided by the Office upon request and payment of the necessary fee.
1. Lamp
1.1 : Front
1.2 : Perspective
1.3 : Bottom
The areas shown in blue depict portions of the lamp that form no part of the claimed design.