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
t = input()
for T in xrange(t):
        n = input()
        l = []
        m = [0]*26
        maxx = 0
        ans = ''
        for i in xrange(n):
                l.append({})
                s  = raw_input()
                for char in s:
                        if char not in l[i]:
                                l[i][char] = 1
                                m[ord(char)-97] += 1
        for i in xrange(26):
                if m[i] > maxx:
                        maxx = m[i]
                        ans = chr(i+97)
        print ans