Base Plans

After fixing the mercury leak, Kim has arrived in the planning room, where he finds a square map of a field, with $N$ rows and $N$ columns. Each cell in the field is either empty, or has a lookout tower on it. Using his notes, he immediately realises that this field is where the JSA will build their new base! Kim knows that Soum is a fan of symmetric base design, and will only approve of a base t