Inside a square of area $$36 \text{ cm}^2$$, there are shaded regions as shown. The ratio of the shaded area to the unshaded area is $$3 \colon 1$$. What is the value of $$a + b + c + d$$ where a, b, c, d are the lengths of the bases of the shaded regions ? Further, if three of a, b, c, d are equal integers and one different, then find them.