If \left[ {\matrix{
1 & 1 \cr
0 & 1 \cr
} } \right]\left[ {\matrix{
1 & 2 \cr
0 & 1 \cr
} } \right]\left[ {\matrix{
1 & 3 \cr
0 & 1 \cr
} } \right]....\left[ {\matrix{
1 & {n - 1} \cr
0 & 1 \cr
} } \right] = \left[ {\matrix{
1 & {78} \cr
0 & 1 \cr
} } \right],
then the inverse of \left[ {\matrix{
1 & n \cr
0 & 1 \cr
} } \right] is