If $-2\le \left[x\right]<2,-1\le \left[y\right]<1,-3\le \left[z\right]<3$ 

where $\left[.\right]$ denotes the greatest integer function 

then minimum value of the determinant $\Delta =\left|\begin{array}{l}\left[x\right]+1 \left[y\right]\left[z\right]\\ \left[x\right] \left[y\right]+1\left[z\right]\\ \left[x\right] \left[y\right]\left[z\right]+1\end{array}\right|$ is