The ornamental design for a cup, as shown and described.
FIG. 1 is a front, perspective view of a cup showing our new design;
FIG. 2 is a front view thereof, the rear view being a mirror image thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The features shown in broken lines are portions of the cup forming no part of the claimed design. The features shown in long dash-short dash bolded broken lines indicate the bounds of the claimed design and otherwise form no part of the claimed design.