Developers often face with regular expression patterns. A pattern is usually defined as a string consisting of characters and metacharacters that sets the rules for your search. These patterns are most often used to check whether a particular string meets the certain rules.

In this task, a pattern will be a string consisting of small English letters and question marks ('?'). The question mark in the pattern is a metacharacter that denotes an arbitrary small letter of the English alphabet. We will assume that a string matches the pattern if we can transform the string into the pattern by replacing the question marks by the appropriate characters. For example, string aba matches patterns: ???, ??a, a?a, aba.

Programmers that work for the R1 company love puzzling each other (and themselves) with riddles. One of them is as follows: you are given *n* patterns of the same length, you need to find a pattern that contains as few question marks as possible, and intersects with each of the given patterns. Two patterns intersect if there is a string that matches both the first and the second pattern. Can you solve this riddle?
The first line contains a single integer *n* (1 ≤ *n* ≤ 10<sup class="upper-index">5</sup>) — the number of patterns. Next *n* lines contain the patterns.

It is guaranteed that the patterns can only consist of small English letters and symbols '?'. All patterns are non-empty and have the same length. The total length of all the patterns does not exceed 10<sup class="upper-index">5</sup> characters.

# Problem: C. Pattern
# Contest: Codeforces - Coder-Strike 2014 - Round 1
# URL: https://codeforces.com/contest/412/problem/C
# Memory Limit: 256 MB
# Time Limit: 1000 ms
# Powered by CP Editor (https://github.com/cpeditor/cpeditor)

from sys import stdin
def get_ints(): return list(map(int, stdin.readline().strip().split()))

n = int(input())

ar = [input() for i in range(n)]
chr = 'x'
res = ""
for i in range(len(ar[0])):
	s = set([x[i] for x in ar])
	k = len(s)
	if k ==1 and '?' in s:
		res+=chr
	elif k == 1 and '?' not in s:
		res+=list(s)[0]
	elif k == 2 and '?' in s:
		res+= [x for x in s if x !='?'][0]
	elif k >= 2 and '?' not in s:
		res+="?"
print(res)