What is claimed is the ornamental design for a carton, as shown and described.
FIG. 1 is a perspective view of a carton, showing the new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a left-side elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a right-side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a top plan view thereof, illustrated in a flat configuration, bottom plan view being a mirror image thereof, it being understood that the thickness of the design in the flat configuration is the thickness of the material as shown in the other figures.