The ornamental design for a ring, as shown and described.
1. Ring
1.1 : Front
1.2 : Back
1.3 : Right
1.4 : Left
1.5 : Top
1.6 : Bottom
1.7 : Perspective
Reproduction 1.1 is a front view of the ring, reproduction 1.2 is a rear view of the ring, reproduction 1.3 is a right view of the ring, reproduction 1.4 is a left view of the ring, reproduction 1.5 is a top view of the ring, reproduction 1.6 is a bottom view of the ring, reproduction 1.7 is a perspective view of the ring.