You've been invited, and agree to join a few close friends on a week-long camping trip to a cabin in the woods.
After everyone is settled in, on the first morning, pancakes are on the menu for breakfast. In order to make enough for everyone, Cookie tells you to fetch exactly 2 gallons of water from the well.
When you get to the well, you find only two jugs, one marked "7 Gallons" and the other, "13 Gallons." You have no other measuring devices.
How do you return with exactly 2 gallons of water?
