def get_usa_acc_id(year, case_index):
    """
    Returns global accident id for USA, year and index of accident.
    USA ids will be in form 1200700000001234
    1 at the beginning means it is from USA
    2007 means the year
    1234 means the case ID as in FARS data
    """
    try:
        acc_id = 1000000000000
        acc_id += year * 100000000
        acc_id += case_index
    except KeyError:
        raise ValueError("Country code incorrect")
    return acc_id