Let a line perpendicular to the line \( 2x - y = 10 \) touch the parabola \( y^{2} = 4(x - 9) \) at the point \( P \). The distance of the point \( P \) from the centre of the circle \( x^{2} + y^{2} - 14x - 8y + 56 = 0 \) is \( \_\_\_\_\_\_\_ \).