An elephant is trapped in a room made of concrete blocks. Three of the walls are reinforced with steel, but one wall is not.

The elephant selected a wall and charged with all his might, but the wall was reinforced, and did not budge.

The elephant charged a second wall, but that wall was also reinforced and did not budge. The elephant grunted from the pain of bouncing off.

After a pause, the elephant charged another wall. He was hopeful at first, but once again the wall was reinforced and he bounced off painfully.

Catching his breath, he turned to you and said, "I hope you enjoyed this joke."

With the fourth wall broken, he walked away free.