Obviously, x.y and parity are the same, so it can be concluded that if they are both even numbers, then their prime numbers are the same. Let X = 2 s * p, Y = 2 s * q, s ≥ 0, p and q are odd numbers, and the original formula is equal to 4 * 2 [2s] * PQ/2 s [p+q]. /r= odd number, let t? =rm, due to t? Modulo 4 is 1, so R and M are modulo 4 congruences, that is, they are either modulo 4 congruences 1 or modulo 4 congruences 1, and ① modulo 4 congruences 1 give = 2 [2s+2] r-RM = 4n-/kloc-.