There was an island with three kingdoms on it.
Let’s call them A, B and C.
The island had a fresh water lake on it and the lake itself had an island.
The three kingdoms always kept fighting over this island.
One day the three kingdoms decided to settle this dispute once it for all and sent small portions of their armies. Kingdom A sent 15 knights and 25 squires; kingdom B send 20 knights and 25 squires and Kingdom C sent one knight and one squire.
The knights decided among themselves that this fighting was beneath them and decided to let the squires settle things by themselves. While the squires of Kingdom A and Kingdom B were warming up, the squire of Kingdom C erected a tall pole, tied a noose to it and hung a pot in the noose.
When they actually started fighting, the squire of kingdom C was able to successfully fight off all the other squires, because the squire of the high-pot-and-noose is equal to the sum of the squires of the other two sides