A drunk goes to the doctors complaining of tiredness and headaches. ''i feel tired all the time'' he slurs ''my head hurts, i've got a sore backside and i'm not sleeping. what could it be doctor?'' Frowning, the doctor examines him before standing back. ''i can't find anything wrong,'' he says, '' it must be the drinking.'' ''fair enough'' replies the bloke. ''i'll come back when you're sober.''