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
import operator
l=['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z']
for i in xrange(input()):
	n=input()
	x={}
	ma=0
	for a in xrange(n):
		st=raw_input()
		for j in l:
			if j in st:
				try:
					x[j] +=1
				except:
					x[j]=1
	for val in x:
		if x[val]>ma:ma=x[val]
	for val in l:
		try:
			if x[val]==ma:
				print val
				break
		except:
			continue