Large Square

You are given $N$ identical squares, each with side length $A$. All the squares have their sides parallel to the $x-axis$ and $y-axis$. That is, the squares are not tilted. You have to take several (possibly, zero or all) squares and rearrange them to obtain a mega square. The mega square can't have any gap in the enclosed region or have overlapping squares. Also, you cannot rotate any square. Ou