I claim the ornamental design for a safe, as shown and described.
FIG. 1 is a perspective view of another safe of the new design;
FIG. 2 is a front view of the safe of FIG. 1;
FIG. 3 is a rear view of the safe of FIG. 1;
FIG. 4 is a left side view of the safe of FIG. 1;
FIG. 5 is a right side view of the safe of FIG. 1;
FIG. 6 is a top view of the safe of FIG. 1; and,
FIG. 7 is a bottom view of the safe of FIG. 1.
The broken line showing of portions of the safe is included for the purpose of illustrating environmental structure and forms no part of the claimed design.