in ecc secp256k1

1/2 = 57896044618658097711785492504343953926418782139537452191302581570759080747169

7/2 = 57896044618658097711785492504343953926418782139537452191302581570759080747172

57896044618658097711785492504343953926418782139537452191302581570759080747172 / 57896044618658097711785492504343953926418782139537452191302581570759080747169 = 7

So the above method from @sss555 is not work to define the pubkey is odd or even. I already try many use method to separate odd and even but pattern to cyclic odd and even is always same.