431. Wildcards

Time limit per test: 2.5 second(s)
Memory limit: 262144 kilobytes
input: standard
output: standard



You are given a list of files in a directory and need to match a specific subset of these files. You've decided to do that with a single string containing wildcards.

More precisely, each file name is a string consisting of lowercase English letters ('a' through 'z'). You want to craft a string consisting of lowercase English letters, asterisks ('*'), and question marks ('?'). An asterisk matches any sequence of letters (including empty). A question mark matches exactly one letter. See examples for further clarification.

Given a list of file names that you want to match and the list of file names that you don't want to match, output a string (which may include wildcards) that will achieve that.

Input
The first line of the input file contains two integers n and m (1 ≤ n, m ≤ 10) — the number of file names to match and the number of file names not to match, respectively. The next n lines contain file names to match, one per line, each no more than 11 characters long, without any whitespace expect newlines. The next m lines contain file names not to match in the same format. All file names in the input file are different.

Output
Output one string that will do the required matches. The length of that string must not exceed 100. If there're several possible solutions, output any. If there's no solution, output "OOPS" (without quotes) instead.

Example(s)
sample input
sample output
2 2
list
tablexx
dataone
datatwo
*l???




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