We claim the ornamental design for a desk, as shown and described.
FIG. 1 is a perspective view of a desk, showing our new design;
FIG. 2 is an exploded perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left-side elevational view thereof, the right-side elevational view being a mirror image thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines showing desk legs, computer components and desktop monitors in FIG. 1 depict environmental matter and form no part of the claimed design.