One day an old Jewish Pole, living in Warsaw, has his last light bulb burn out. To get a new one he’ll have to stand in line for two hours at the store (and they’ll probably be out by the time he gets there), so he goes up to his attic and starts rummaging around for an old oil lamp he vaguely remembers seeing.

He finds the old brass lamp in the bottom of a trunk that has seen better days. He starts to polish it and (poof!) a genie appears in cloud of smoke.

“Ho ho, Mortal!” says the genie, stretching and yawning, “For releasing me I will grant you three wishes.”

The old man thinks for a moment, and says, “I want Genghis Khan resurrected. I want him to re-unite his Mongol hordes, march to the Polish border, and then decide he doesn’t want the place and march back home.”

“No sooner said than done!” thunders the genie. “Your second wish?”

“Ok. I want Genghis Khan resurrected. I want him to re-unite his Mongol hordes, march to the Polish border, and then decide he doesn’t want the place and march back home.”

“Hmmm. Well, all right. Your third wish?”

“I want Genghis Khan resurrected. I want him to re-unite his –”

“Ok ok ok. Right. What’s this business about Genghis Khan marching to Poland and turning around again?”

The old man smiles. “He has to pass through Russia six times.”

I don't remember where I first heard it, but I got this version here.