The Lunatic and the Doctor

One day a doctor is walking around the wards in a psychiatric hospital. He saw a lunatic running at him with a mango in one hand and a knife in the other. The doctor thought the lunatic was going to kill him so he ran.
After a few minutes the doctor came to the end of a corridor with no doors or windows...he was trapped. He prayed and closed his eyes.
After a moment the lunatic rushed up to the doctor and said:
"Oh, doctor! I'm exhausted. I never thought it would be so difficult to offer you a piece of mango!"
ISHARA