\(1^{st}\) round, September \(28^{th}\), 2013

Mirko has been moving up in the world of basketball, starting as a mere spectator, mastering snack
salesmanship, finally reach the coveted position of the national team coach. He is now facing a difficult
task: selecting the five primary players for the upcoming match against Tajikistan.
Since Mirko is incredibly lazy, he doesn't bother remembering players' names, let alone their actual
skills. That's why he has settled on selecting five players who share the same first letter of their
surnames, so that he can remember them more easily. If there are no five players sharing the first letter
of their surnames, Mirko will simply forfeit the game!
In order to obtain insight into possibilities for his team, Mirko wants to know all the different letters
that his primary team's surnames may begin with.

The first line of input contains the positive integer N (\(1 \le N \le 150\)), the number of players that Mirko
has available.
Each of the following N lines contains one word (at most 30 characters long, consisting only of
lowercase English letters), a surname of one of the players.

If there are no five players that Mirko can select matching his criteria, output a single line containing
the word “PREDAJA”^{1} (without quotes). Otherwise, output all possible first letters of representation
player surnames, sorted lexicographically, in a single line with no spaces.

생성자가 기록되지 않았습니다.

출처 COCI 2013/2014 Contest 1