Suppose you need to deliver 40 terabytes of data to your co-workers in Atlanta (200 km). You have an available 100 Mbps dedicate
d link for data transfer. Alternatively, your friend raises homing pigeons and would be willing to let you borrow one. You have a single 1 TB SD card you can strap to the pigeon. Assume pigeons can fly 1000 km per day and that it takes no time to copy to/from the SD card.
The length from Point A to Point D is 6 units, while the length from point A to Point C is 7 units, and the length from Point A to Point B is also 7 units. Because to reach Point C, you have to make one turn, adding one more unit. Same with Point B.