P6535 [COCI 2013/2014 #1] TRENER

There are some strings, and you need to count them according to specific requirements.

You are given $n$ strings. Each string has its corresponding first letter. Output the number of first letters whose corresponding number of strings is at least $5$.

The first line contains a positive integer $n$. The next $n$ lines each contain a string consisting only of lowercase letters, with length not exceeding $30$ characters.

If there is no first letter that meets the requirement, output `PREDAJA`. Otherwise, output all such first letters in lexicographical order, with no spaces.

#### Explanation for Sample 1 The first letters that meet the requirement are `k` and `b`. ------ #### Constraints For $100\%$ of the testdata, $1\le n\le 150$. ------------ #### Notes $\mathtt{Subtask\ 0}$ is the sample. $\mathtt{Subtask\ 1\sim 2}$ has no special restrictions. **This problem is translated from [COCI2013-2014](https://hsin.hr/coci/archive/2013_2014/) [CONTEST #1](https://hsin.hr/coci/archive/2013_2014/contest1_tasks.pdf) T1 _TRENER_.** Translated by ChatGPT 5