A man comes into a restaurant at 6 o'clock in the evening.

"I want to have a coffee please." The waiter brings him the coffee, the man drinks it and afterwards, he orders another, then another, then another. Finally, at 7:30, the man has drunk 5 coffees.

Said the waiter to the man, when he took care of his bill, "When I drink so much coffee in the evening, I cannot sleep half of the night."

"No problem, said the man, I count until three - and then I sleep."

"And that works everytime?" asks the waiter.

"No, sometimes, I count until half past three."