input: Write a Python function to calculate the highest possible score in a m x n grid, where each cell contains a positive integer. You can only move from one cell to another that is either directly below or to the right (not necessarily adjacent). The score of a move from cell c1 to cell c2 is given by the difference c2 - c1. You must start from any cell and make at least one move. The function should return the maximum combined score obtainable.
  
  Here's an example of how the function would be used:
  
  
  from typing import List
  
  def calculate_max_score(grid: List[List[int]]) -> int:
      """
      This function takes an m x n matrix grid with positive integers. Movements are allowed from one cell to any other cell
      directly below or to the right. The score of a move is calculated as the difference between the values of the two cells. 
      Starting from any cell, you must make at least one move and the function returns the highest possible cumulative score.
  
      Examples:
      >>> grid = [[9,5,7,3],[8,9,6,1],[6,7,14,3],[2,5,3,1]]
      9
      >>> grid = [[4,3,2],[3,2,1]]
      -1
  
      Constraints:
      m == grid.length
      n == grid[i].length
      2 <= m, n <= 1000
      4 <= m * n <= 10^5
      1 <= grid[i][j] <= 10^5
      """
  
output: def calculate_max_score(grid: List[List[int]]) -> int:
      m, n = len(grid), len(grid[0])
      max_score = float('-inf')
  
      for i in range(m):
          for j in range(n):
              for i2 in range(i + 1, m):
                  score = grid[i2][j] - grid[i][j]
                  if score > max_score:
                      max_score = score
                      
              for j2 in range(j + 1, n):
                  score = grid[i][j2] - grid[i][j]
                  if score > max_score:
                      max_score = score
                      
      return max_score