input: Write a python function to find the maximum contiguous subarray sum.
  assert max_contiguous_sum([1, -2, 3, 4, -1, 2, 1, -5, 4]) == 9
  assert max_contiguous_sum([-2, 1, -3, 4, -1, 2, 1, -5, 4]) == 6
  assert max_contiguous_sum([5, 4, -1, 7, 8]) == 23
output: def max_contiguous_sum(arr):
      max_sum = arr[0]
      current_sum = arr[0]
      
      for num in arr[1:]:
          current_sum = max(num, current_sum + num)
          max_sum = max(max_sum, current_sum)
      
      return max_sum