The rank of the matrix $\left[\begin{array}{cccc}6 & 0 & 4 & 4 \\ -2 & 14 & 8 & 18 \\ 14 & -14 & 0 & -10\end{array}\right]$ is
The rank of the matrix $\left[\begin{array}{cccc}6 & 0 & 4 & 4 \\ -2 & 14 & 8 & 18 \\ 14 & -14 & 0 & -10\end{array}\right]$ is