Jack was very fat and his wife was worried about him, so she made him see the doctor...

The doctor weighed him and said, "You must lose 30 kg. Eat only fruits and vegetables and jog 5 km a day for the next 100 days. Then give me a call and tell me how much you weigh." Jack went home and did what the doctor told him. 100 days later, Jack called the doctor. "Jack here. You will be happy to know that I have lost 30 kg." "Excellent," said the doctor. "There is just one problem," Jack said. "I am 500 km from home!"