BT 3: WaterYou have a flag. You have a desert. You have a large supply of food and water. You have a number of friends willing to help you.
Your challenge is to carry the flag and plant it at a distance of a four-day march into the interior of the desert (without loss of life), using the least amount of water possible. Carrying the flag and food is not the issue. The problem is water: a person can carry a maximum of five days' worth of water at any given time.
What is the least amount of water that it requires to plant the flag and return?