def city_code(city):
    """
    :param city: city is a custom slot type in the alexa skill configuration
    possible values are:
    Helsinki
    Helsingfors
    Espoo
    Esbo
    Vantaa
    Vanda
    Kauniainen
    Grankulla
    :return: a short code is in HSL bus stops. "" for Helsinki, "E" for Espoo
    "V" for Vantaa and "Ka" for Kauniainen
    """
    lc_city = city.lower()
    if lc_city == "helsinki" or lc_city == "helsingfors":
        return ""
    elif lc_city == "espoo" or lc_city == "esbo":
        return "E"
    elif lc_city == "vantaa" or lc_city == "vanda":
        return "V"
    elif lc_city == "kauniainen" or lc_city == "grankulla":
        return "Ka"
    else:  # silently default to Helsinki
        return ""