The ornamental design for a laptop, as shown and described.
FIG. 1 is a bottom view of a laptop showing the new design;
FIG. 2 is a left side view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side perspective view thereof;
FIG. 5 is an enlarged section thereof as shown in FIG. 1;
FIG. 6 is an enlarged section thereof as shown in FIG. 2;
FIG. 7 is another enlarged section thereof as shown in FIG. 2; and,
FIG. 8 is an enlarged section thereof as shown in FIG. 3.
Views of the laptop which are not depicted in the figures do not comprise claimed subject matter, the features shown in broken lines depict environmental subject matter only and form no part of the claimed design.