def GetEffectiveRootAdUnitId(client, server, version):
  """Get the effective root ad unit ID.

  Args:
    client: DfpClient used for service creation.
    server: str the API server.
    version: str the API version.

  Returns:
    The effective root ad unit ID.
  """
  network_service = client.GetService('NetworkService', server, version)
  return network_service.GetCurrentNetwork()[0]['effectiveRootAdUnitId']