// **Problem:**
// You are given a 2D grid representing a map of land and water.
// Each cell in the grid contains an integer representing the elevation of the land.
// The Pacific Ocean touches the left and top edges of the grid, and the Atlantic Ocean touches the right and bottom edges.
// Water can only flow from a cell to another if and only if the elevation of the latter is equal to or lower than
// the former. Determine the coordinates where water can flow from both the Pacific and Atlantic oceans.
// Write a function to find all coordinates where water can flow to both the Pacific and Atlantic oceans.
// **Examples:**
// Consider the following 5x5 grid representing the elevation map:
// ```
// Pacific
// |
// 1 2 2 3 5
// 3 2 3 4 4
// 2 4 5 3 1
// 6 7 1 4 5
// 5 1 1 2 4 __Atlantic
// ```
// Input: [[1,2,2,3,5],[3,2,3,4,4],[2,4,5,3,1],[6,7,1,4,5],[5,1,1,2,4]]
// Output: [[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]
// {(4, 4), (3, 4), (3, 1), (1, 4), (4, 2), (2, 3), (3, 3), (1, 3)}
// {(1, 2), (2, 1), (3, 1), (1, 1), (1, 3)}
// **Constraints:**
// The grid dimensions m×n are such that 1≤m, n≤200, 1≤m, n≤200.
// Each element in the grid represents an integer elevation value.
// The elevation values are non-negative integers.