input: Write a python function to find the largest consecutive sum in a list of integers.
  assert largest_consecutive_sum([1, 2, 3, -2, 5])==9
  assert largest_consecutive_sum([-2, -3, 4, -1, -2, 1, 5, -3])==7
  assert largest_consecutive_sum([1, 2, 3, 4, 5])==15
  assert largest_consecutive_sum([-1, -2, -3, -4, -5])==0
output: def largest_consecutive_sum(arr):
      if not arr:
          return 0
  
      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 if max_sum > 0 else 0