计算行列式

$$
D=\left|\begin{array}{ccccc}
x_1 & a_2 & a_3 & \cdots & a_n \\
a_1 & x_2 & a_3 & \cdots & a_n \\
a_1 & a_2 & x_3 & \cdots & a_n \\
\vdots & \vdots & \vdots & & \vdots \\
a_1 & a_2 & a_3 & \cdots & x_n
\end{array}\right|, x_i \neq a_i, i=1,2, \cdots, n
$$