input: from typing import List
  
  def is_balance_negative(operations: List[int]) -> bool:
      """ Given a sequence of bank account operations that starts with an initial balance of zero, determine if 
      the account balance ever goes below zero. If it does, return True. Otherwise, return False.
      >>> is_balance_negative([1, 2, 3])
      False
      >>> is_balance_negative([1, 2, -4, 5])
      True
      """
output:     balance = 0
      for operation in operations:
          balance += operation
          if balance < 0:
              return True
      return False