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06/12/2025 07:35:41
1629. Alphabet
Alphabet
Олимпиадные задачи на английском языке| 04/07/2011 | Лето 2011 - дорешивание (10D) |
| 15/07/2011 | Лето 2011 - 10 (D) |
| 09/01/2017 | Марафон 1 (командный) "Hatter's riddles" (G) |
Ограничения: время – 1s/2s, память – 32MiB Ввод: input.txt или стандартный ввод Вывод: output.txt или стандартный вывод 
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A list of words written in some unknown alphabet was found. It is known, however, that these words
are in alphabetic order. Write a program that will find the unique alphabetic ordering of used letters,
or determine that no such ordering exists or that there is more than one possible solution.
Input
The first line of input contains a positive integer `N` (`N\ ≤\ 100`), the number of words.
The following `N` lines contain the list of words found, one word per line. Each word consists of at
most 10 lowercase letters.
Output
The first and only line of output should contain all letters in alphabetic order. If no such ordering
exists, output ‘!’. If there is more than one solution, output ‘?’.
Sample Input 1
5 ula uka klua kula al
Sample Output 1
luka
Sample Input 2
4 jaja baba baja beba
Sample Output 2
!
Sample Input 3
3 marko darko zarko
Sample Output 3
?
