# 编辑者：闫龙
#三级目录
menu = {
    ‘北京‘:{
        ‘海淀‘:{
            ‘五道口‘:{‘soho‘:{},‘网易‘:{},‘google‘:{}},
            ‘中关村‘:{‘爱奇艺‘:{},‘汽车之家‘:{},‘youku‘:{},},
            ‘上地‘:{‘百度‘:{},},
        },
        ‘昌平‘:{
            ‘沙河‘:{‘老男孩‘:{},‘北航‘:{},},
            ‘天通苑‘:{},
            ‘回龙观‘:{},
        },
        ‘朝阳‘:{},
        ‘东城‘:{},
    },
    ‘上海‘:{
        ‘闵行‘:{
            ‘人民广场‘:{‘炸鸡店‘:{}}
        },
        ‘闸北‘:{
            ‘火车战‘:{‘携程‘:{}}
        },
        ‘浦东‘:{},
    },
    ‘山东‘:{},
}
#定义一个用户输入列表,用来记录用户所输入的
UserSelect=[];
while True:
    if(len(UserSelect)==0):
        for i in menu.keys():
            print(i);
    if(len(UserSelect)==1):
        if(UserSelect[-1] in menu):
            for i in menu[UserSelect[-1]].keys():
                print(i);
        else:
            print("您输入的信息不在列表中");
            UserSelect.pop(-1);
            continue;
    if (len(UserSelect) == 2):
        if (UserSelect[-1] in menu[UserSelect[-2]]):
            for i in menu[UserSelect[-2]][UserSelect[-1]].keys():
                print(i);
        else:
            print("您输入的信息不在列表中");
            UserSelect.pop(-1);
            continue;
    if (len(UserSelect) == 3):
        if (UserSelect[-1] in menu[UserSelect[-3]][UserSelect[-2]]):
            for i in menu[UserSelect[-3]][UserSelect[-2]][UserSelect[-1]].keys():
                print(i);
        else:
            print("您输入的信息不在列表中");
            UserSelect.pop(-1);
            continue;
    UserInput=input(">>>:").strip();
    if(UserInput == "b"):
        if(len(UserSelect) == 0):
            print("已经是最高级了!");
            continue;
        else:
            UserSelect.pop(-1);
    elif(UserInput == "q"):
        exit();
    else:
        UserSelect.append(UserInput);