Three engineers and three accountants are travelling by train to a conference. The accountants take their seats, but the engineers all cram into one toilet and shut the door.Shortly after the train departs, the conductor comes round checking tickets. He knocks on the toilet door and calls "Tickets please". The door opens a crack and a hand comes out holding a ticket, which is duly checked. The accountants see this and agree it's a good idea.After the conference, the accountants decide to try the trick and save some money.When they get to the station, they therefore just buy one ticket. However, to their amazement, the engineers don't buy any tickets at all."How are you going to travel without any ticket?", an amazed accountant asks.... "Watch and see!", comes the reply.So, when they get on the train, the accountants cram into one toilet and the engineers all crowd into one nearby. The train departs.Shortly afterwards, one of the engineers leaves their toilet and walks over to the one that contains the accountants.He knocks on the door and says "Tickets please!"