You are given an `R x C` grid of integers representing elevations. A skier starts at a given cell `(sr, sc)`. From a cell, the skier may move up/down/left/right to a neighboring cell with **strictly lower** elevation. The skier can continue moving as long as the elevation strictly decreases. Define the skier’s score as the **maximum number of cells** that can be visited in a valid downhill run starting from `(sr, sc)` (including the start cell). Tasks: 1. Return the maximum possible score for a single skier starting at `(sr, sc)`. 2. Follow-up: if you are given **many skiers** (a list of starting cells), return the score for each efficiently. State your time/space complexity for both the single-skier and multi-skier versions.