3. A three-digit number, where the hundreds and units digits are the same, and this three-digit number is a perfect square. There are $\qquad$ such three-digit numbers.

Note: A perfect square can be expressed in the form of $a \times a$, such as $9=3 \times 3, 25=5 \times 5$, both 9 and 25 are perfect squares.
$3$