Because A is a finite set of n elements, A×A-* * has n square ordered pairs, and the binary relations on A are all subsets of A×A, the number of which is 2 to the n power. Therefore, when finding the power of R, you will only get two different relationships with the power of the square of N at most, so there must be repeated powers, that is, the power of S of R = the power of T of R, where 0