Three men, an English man, an American and a French man, when one of them discovers a bottle. He rubs it and out pops a very grateful genie who grants them a wish each.
The American goes first. "I love my country and want to help the world. I wish America could produce enough grain to feed everyone."
"A good and noble wish," says the genie as he grants it.
The French man is next, "I too love my country but we have been invaded too often. I want to protect my country. Build a wall around it."
The genie says, "Good wish," and grants it.
Finally, the English man. "Tell me a bit more about this wall around France."
"It's thirty feet high and fifteen feet thick," says the genie. "It is continuous without a single gap."
"Great," says the English man. "Fill it with water."