The ornamental design for a cup, as shown and described.
FIG. 1 is a top perspective view of a cup, showing our new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a left side view thereof, the right side view being the same;
FIG. 4 is a front view thereof, the rear view being the same;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is a top view thereof.
The broken lines in the figures illustrate the portions of the design that form no part of the claimed design. The dot-dash broken lines immediately adjacent to the claimed areas in the views represent the boundaries of the design and form no part thereof. None of the broken lines form any part of the claimed design.