a duck walks into a bar and asks the barman "can i have a beer and a cheese sandwitch please?" and the barman says "i can give you a beer but we don't do cheese sandwitches." so the duck sits down, has its beer and 10 minutes later goes back to the barman and asks "can i have a beer and a cheese sandwitch please?" to this, the barman replied "i already told you, we don't do cheese sandwitches, but here is your beer." so the duck sits down, as its beer and 10 minutes later it goes back to the barman and asks "can i have a beer and a cheese sandwitch please?" and the barman says "here's your beer, but if you ask for a cheese sandwitch 1 more time, i'll nail your beak to the bar." so the duck sits down, has its beer and goes back to the barman who says "what do you want?" the duck asks "do you have any nails?" the barman replys "no." then, the duck says "then i'll have a cheese sandwitch and a beer please!"