def gen_city_dancers_D(dni_dan_D, dni_D, dance):
    D = {}
    for dni, dan_L in dni_dan_D.items():
        if dance in dan_L:
            udt_city_dancers_D(D, dni, dni_D)
    # dlli_ord(D)
    return D
            
def udt_city_dancers_D(D, dni, dni_D):
    if dni in dni_D:
        name, city = dni_D[dni]
    else:
        name, city = dni, 'Unknown'
    if city not in D:
        D[city] = [name]
    else:
        D[city].append(name)
    
def ord_city_dancers_D(dloc):
    for l in dloc.values():
        l.sort()