Fast Cars

Harvey loves cars. He enjoys racing them. As expected, he has a garage full of cars. He, along with his friends, go to the racetrack during the weekends to race these cars. Harvey wants his friends to enjoy the race and so he wants the race to be close. This can happen only if the cars are comparable on their top-speed i.e. the difference in their top-speed is less. There are N cars in the garage.