If the product of  n matrices $\left[\begin{array}{cc}1& 1\\ 0& 1\end{array}\right]\left[\begin{array}{cc}1& 2\\ 0& 1\end{array}\right]\left[\begin{array}{cc}1& 3\\ 0& 1\end{array}\right]........\left[\begin{array}{cc}1& \mathrm{n}\\ 0& 1\end{array}\right]$ is equal to the matrix $\left[\begin{array}{cc}1& 378\\ 0& 1\end{array}\right]$, the value of n is equal to