We Need A Doctor

A girl was walking on the side walk. She sees a man lying on the street, needing immediate help. The victim says that he is having a heart attack. The girl asks people around the street. And a man approached. Girl: Help, are you a doctor? Man: I am a doctor. What’s going on? Girl: A Heart Attack! Man: I am doctor in mathematics. Girl: He is going to die. Man: Prove it!