menu = {
    "山东": {
        "济南": {
              "平阴": {},
              "商河": {},
              "莱芜": {}
         },
        "济宁": {
              "金乡": {},
              "微山": {},
              "嘉祥": {}
        },
        "曲阜": {
              "南辛": {},
              "陵城": {},
              "防山": {}
        }
    },
    "北京": {
        "海淀": {
                "万寿路": {},
                "永定路": {},
                "中关村": {}
       },
        "昌平": {
                "回龙观": {},
                "南口": {},
                "沙河": {}
        },
        "朝阳": {
                "呼家楼": {},
                "三里屯": {},
                "双井": {}
        }
    },
    "上海": {
        "黄浦": {
                "南京东路": {},
                "外滩": {},
                "瑞金二路": {}
        },
        "徐汇": {
            "湖南路": {},
            "天平路": {},
            "枫林路": {}

        },
        "长宁": {
                "华阳路": {},
                "新华路": {},
                "江苏路": {}
        }
    },
}
def three(dic):
    while True:
        for k in dic:print(k)
        key = input('input>>').strip()
        if key == 'b' or key == 'q':
            return key
        elif key in dic.keys() and dic[key]:
            ret = three(dic[key])
            if ret == 'q':
                return "q"
        elif (not dic.get(key)) or (not dic[key]):
            continue
three(menu)