Phone List  
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Given a list of phone numbers, determine if it is consistent in the sense that no number 
is the prefix of another. Let's say the phone catalogue listed these numbers: 

Emergency 911 
Alice 97 625 999 
Bob 91 12 54 26 

In this case, it's not possible to call Bob, because the central would direct your call 
to the emergency line as soon as you had dialled the first three digits of Bob's phone 
number. So this list would not be consistent. 

Input
-----  
The first line of input gives a single integer, 1 <= t <= 40, the number of test cases. 
Each test case starts with n, the number of phone numbers, on a separate line, 1 <= n <= 10000. 
Then follows n lines with one unique phone number on each line.  A phone number is a sequence 
of at most ten digits. 

Output
------  
For each test case, output YES if the list is consistent, or NO otherwise. 

Sample Input  
------------
2 
3 
911 
97625999 
91125426 
5 
113 
12340 
123440 
12345 
98346

Sample Output  
-------------
NO 
YES