A: My brother smokes three packs a day.
B: Three packs of what?
A: Cigarettes, of course.
B: How can he do that?
A: When he is almost finished with one cigarette, he uses it to light another.
B: He's a chain smoker.
A: He's been a chain smoker for 30 years.
B: That's unbelievable. Can he still breathe?
A: He can, but the people around him can't.
B: How can he still be alive?
A: His doctor says his heart and lungs are strong and healthy.
B: Maybe I should start smoking.