The ornamental design for a scarf, as shown and described.
FIG. 1 is a front view of the scarf in an open configuration;
FIG. 2 is a back view of the scarf of FIG. 1;
FIG. 3 is a left side view of the scarf of FIG. 1;
FIG. 4 is a right side view of the scarf of FIG. 1;
FIG. 5 is a top view of the scarf of FIG. 1;
FIG. 6 is a bottom view of the scarf of FIG. 1;
FIG. 7 is a perspective view of the scarf of FIG. 1, with the scarf shown in a deployed configuration and as worn by a user;
FIG. 8 is a front view of the scarf of FIG. 7;
FIG. 9 is a back view of the scarf of FIG. 7;
FIG. 10 is a left side view of the scarf of FIG. 7; and,
FIG. 11 is a right side view of the scarf of FIG. 7.
The human figure rendered by broken lines depicts unclaimed environmental structure. The areas of the scarf rendered by broken lines define portions of the scarf that form no part of the claimed design. The dash-dot-dash broken lines define bounds of the claimed design and form no part thereof. All illustrated broken lines form no part of the claimed design.