class TalkingStick:
    def __init__(self):
        self.chat_by_talking = dict()
        self.talking_by_chat = dict()

    def holder(self, cid):
        return self.talking_by_chat[cid]

    def take(self, uid, cid):
        self.chat_by_talking[uid] = cid
        self.talking_by_chat[cid] = uid

    def aho(self, uid):
        cid = self.chat_by_talking[uid]
        del self.talking_by_chat[cid]
        del self.chat_by_talking[uid]