modular arithmetic - Show that $p$ must be congruent to either 1 or 4 modulo 5

Let $p$ be a prime number $(p \neq 2$ and $p \neq5)$, and let $A$ be some given number.
Suppose that $p$ divides the number $A^2 - 5$. Show that $p$ must be congruent to either 1 or 4 modulo 5.

A little confused about this number theory question. Any Help? I would love to see a solution to this problem. Thanks.