The ornamental design for a slipper, as shown and described.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
1. Slipper
1.1: Perspective
1.2: Front
1.3: Back
1.4: Top
1.5: Bottom
1.6: Left
1.7: Right
1.8: Top in an alternate position
The portion of the design shown in the color yellow is for the purpose of illustrating a portion of the slipper and forms no part of the claimed design.