Czech ACM Student Chapter
Czech Technical University in Prague
Charles University in Prague
Technical University of Ostrava
Slovak University of Technology
CTU Open Contest 2007
identity.c, identity.C, identity.p, identity.java
Beside other services, ACM helps companies to clearly state their "corporate identity", which
includes company logo but also other signs, like trademarks. One of such companies is Internet
Building Masters (IBM), which has recently asked ACM for a help with their new identity. IBM
do not want to change their existing logos and trademarks completely, because their customers
are used to the old ones. Therefore, ACM will only change existing trademarks instead of
creating new ones.
After several other proposals, it was decided to take all existing trademarks and find the longest
common sequence of letters that is contained in all of them. This sequence will be graphically
emphasized to form a new logo. Then, the old trademarks may still be used while showing the
Your task is to find such a sequence.
The input contains several tasks. Each task begins with a line containing a positive integer N,
the number of trademarks (2 . N . 4000). The number is followed by N lines, each containing
one trademark. Trademarks will be composed only from lowercase letters, the length of each
trademark will be at least 1 and at most 200 characters.
After the last trademark, the next task begins. The last task is followed by a line containing
For each task, output a single line containing the longest string contained as a substring in all
trademarks. If there are several strings of the same length, print the one that is lexicographically
smallest. If there is no such non-empty string, output the words "IDENTITY LOST"instead.
Output for Sample Input