class Message {
    int currId;
    string text;
public: 
    Message() : currId{0}, text{} {}
    Message(int id, const string &msgText) : currId{id}, text{msgText} {}
    
    const string& get_text() const {
        return text;
    }
    
    friend bool operator<(const Message &lhs, const Message &rhs)
    {
        return lhs.currId < rhs.currId;
    }
};

class MessageFactory {
    int msgId = 0;
public:
    MessageFactory() {}
    Message create_message(const string& text) {
        return Message{msgId++, text};
    }
};