Square is an operation. For example, the square of a is represented by a×a, which is abbreviated as a². It can also be written as a×a (a to the first power × a to the first power = a to the second power). For example, 4×4=16, 8×8=64, and the square symbol is 2. That is, 2 squared is 4, which is equal to 2×2=4.

According to legend, an Indian minister invented chess and presented it to the king. The king was very grateful and agreed to meet his request: put rice grains on the chessboard. Put 1 grain on the first square, 2 grains on the second square, then 4 grains, 8 grains, 16 grains... until 64 grains are put on the chessboard.

The king laughed and thought he was a fool for thinking that such a small amount of rice was all that was needed.

Is this really the case? According to the minister's request, to fill 64 squares, you need 1+2+2²+2³+…+2⁶³=2⁶⁴-1 grain. This number is 18,446,744,073,709,551,615, a 20-digit number. Not to mention emptying the national treasury, even the rice in the whole of India, or even the whole world, cannot satisfy the minister's demands!