input: 
  from typing import List
  
  def find_gcd(numbers: List[int]) -> int:
      """ Find the Greatest Common Divisor (GCD) of a given list of integers.
      >>> find_gcd([1000, 500])
      500
      >>> find_gcd([8, 12, 20])
      4
      """
      def gcd(a: int, b: int) -> int:
          if b == 0:
              return a
          return gcd(b, a % b)
      
      if not numbers:
          return 0
      result = numbers[0]
      for num in numbers[1:]:
          result = gcd(result, num)
          if result == 1:
              return 1
      return result
  
output:     if not numbers:
          return 0
      result = numbers[0]
      for num in numbers[1:]:
          result = gcd(result, num)
          if result == 1:
              return 1
      return result