I was trying to do the following.
Construct suffix automation for each command.
Binary search for length of each key substring.
Binary search works as follows.
For each substring of command of len (lower_bound+upper_bound) /2 check whether it is a substring of another command.

And it was Time Limit Exceed #7.
So, don't repeat yourself.  Find better solution.
Probably with suffix array,  as posted on the webboard.