Hello, I am going to a conference in Ottawa, but before going to the conference, I will spend a weekend in Montreal. The conference starts on Tuesday, so my question is: could I buy the bus tickets the same day to Ottawa or I have to buy them in advance? I prefer to buy them the same day since I am not sure if I would like to spend the whole Monday in Montreal and then arrive late to Ottawa or I would choose to take the early bus and arrive soon to Ottawa. Since I have never been to Montreal, I do not want to commit to leave in a certain schedule for later having regrets. Any advice?