The rank of matrix \(\begin{bmatrix} k & -1 & 0 \\[0.3em] 0 & k & -1 \\[0.3em] -1 & 0 & k \end{bmatrix}\) is 2, for \( k = \)
The rank of the matrix\(\begin{bmatrix} 1 & 1 & 1 \\[0.3em] a & a^2 & a^3 \end{bmatrix}\) is ____ .