A smoker comes to the doctor's practice, then the doctor advises him not to smoke and says:
Doctor: "How many years have you been smoking?"
Patient: "30 years I smoke"
Doctor: "One day how many packs of cigarettes do you spend"
Patient: "Two packs of cigarettes usually"
Doctor: "How much is the price of a pack of cigarettes?"
Patient: "10 Dollars"
Doctor: "Try to see the big building over there!" (While showing out the window
Then the patient sees it.
Patient: "really a beautiful building expensive"
Doctor: "Try to count one day you spend 2 packs of cigarettes at a price of USD $ 20 and for 30 years you smoke. You will be able to buy the building, if you keep it"
Patient: "Doctor smoking no?"
Doctor: "no"
Patient: "Have doctors been able to buy a luxury building"
Doctor: "No"
Patient: "Same as me"