Let r^2-ms^2 \in \mathbb {Z} , and suppose that m is a square free integer with r,s not integers, prove that  m \equiv 1 \ (mod \ 4)

Proof so far.

I have r^2-ms^2 = n \ \ \ \ \ n \in \mathbb {Z}
 m = \frac {r^2-n}{s^2}