there is a car near to a desert with width of 563Km.
and there is a gas station at the left border of the desert.
the car could take 315L gas at most one time.
it can store the gas in the desert for a longer trip.
now, how much gas it need at least to go through the desert?
from the internet, I got a answer 1575. but it's not 1575 in my analysis.
