Can we use Gauss's Lemma ?

To determine whether the given number is quadratic residue , consider the list :

If the number of the elements in the above list lying between and inclusively is even , then is quadratic residue , otherwise , it is quadratic non-residue .

In this case , and is either or

The elements lying between the range should be :

for so the number is an odd number .

Or

for so the number is also an odd .

Therefore , is not the quadratic residue of modulo .

Remarks : so we can see that is quadratic residue of modulo .