The determinant of the matrix $$A = \left[\begin{array}{rrrrrrrrr} 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ 1 &2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ \end{array}\right]$$ is .
Hint: Remember that a square linear system has a unique solution if the determinant of the coefficient matrix is non-zero.