input: from typing import List
  
  
  def is_balance_negative(operations: List[int]) -> bool:
      """ Provided a sequence of deposit and withdrawal operations on a bank account starting with
      a zero balance, determine if the account balance ever drops below zero. The function should return
      True if it does, otherwise it should 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