Long ago, there was a king in India whose favorite game was chess.
One day, a wise old man visited the kingdom. The king challenged him to a game and promised, "You may claim any prize if you win."
The old man replied, "If I win, I would like one grain of rice for the first square on the chessboard, two for the second, four for the third, and then double the amount for each subsequent square."
"Is that all?" asked the king, surprised. "Would you not prefer gold or silver instead?"
"No," the old man said firmly. "Just rice."
They played for a long time, and finally, the old man won. The king ordered his servants to bring a bag of rice. He placed one grain on the first square, two on the second, and continued doubling the amount for each new square. The king soon realized the grave problem: even with all the rice in his kingdom, there would not be enough to cover all 64 squares of the chessboard.