Find the determinant of the matrix $$A=\left [ \matrix { -6 & -5 & & \cdots & -5 \\ -5 & -6 & -5 & \cdots & -5 \\ & & \ddots & & \\ -5 & \cdots & -5 & -6 & -5 \\ -5 & \cdots & & -5 & -6 \\ }\right] \in \mathbb{R}^{79\times 79}.$$
$\det(A) =$