The desert lies before you. Your mission is to plant a flag a four daysí march into the interior. You do not have any special equipment and must rely on your own powers. Carrying food and the flag itself is not a problem. The only limitation has to do with water: you can carry only a five-day supply of water. Thus, the amount of water you could bring with you would take you only two and a half days toward your destination and back to your
starting point. Given these conditions, how can you fulfill your mission using at most a twelve-day supply of water? (You can assume that
you have plenty of water at the starting point.)