$n$ 阶行列式 $\left| \begin{array}{ccccc}2 & 0 & \dots & 0 & 2\\ -1 & 2 & \dots & 0 & 2\\ \vdots & \vdots & & \vdots & \vdots \\ 0 & 0 & \dots & 2 & 2\\ 0 & 0 & \dots & -1 & 2 \end{array} \right| = \underline{\quad}$