Let the centre of the circle $$x^2 + y^2 + 2gx + 2fy + 25 = 0$$ be in the first quadrant and lie on the line $$2x - y = 4$$. Let the area of an equilateral triangle inscribed in the circle be $$27\sqrt{3}$$. Then the square of the length of the chord of the circle on the line $$x = 1$$ is _______.