You have been given a set of N strings S1, S2, .... SN. Consider any non-empty string S (S need not belong to the given set of N strings). Suppose S occurs (as a substring) in K out of the N given strings in the set. Your job is to choose S such that the value of K is maximized. If there are many such strings, choose the one with the least length. If there are many such strings with the least length, choose the lexicographically smallest of them all.

Input:

The first line consists of T the number of test cases.
The first line in each test case consists of N, the number of words in the given set. Each of the next N lines contains a single word consisting of lowercase English alphabets (a-z) only.

Output:

Print the answer to each test case on a new line, the answer to each test case being a single string S as described in the problem above.

Constraints :

1 ≤ T ≤ 5

1 ≤ N ≤ 100

1 ≤ |Si| ≤ 100, |Si| denotes the length of the input words.

Author : Himanshu

Tester : Shreyans

(By IIT Kgp HackerEarth Programming Club)

SAMPLE INPUT
1
1
shades

SAMPLE OUTPUT
a
from collections import OrderedDict
t= input()
while t:
	t-=1
	n=input()
	re=""
	while n:
		n-=1
		s=raw_input()
		s= list(OrderedDict.fromkeys(s))
		for s in s:
			re+=s
	#print re
	max=0
	new=list(OrderedDict.fromkeys(re))
	new.sort()
	#print new
	for x in new:
		if re.count(x)>max:
			#print re.count(x),
			max=re.count(x)
			final=x
	print final