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.
import sys

#input functions
readint = lambda: int(sys.stdin.readline())
readints = lambda: map(int,sys.stdin.readline().split())
readar = lambda: list(map(int,sys.stdin.readline().split()))
flush = lambda: sys.stdout.flush()

def t(a,i):
    hit = False
    r = "a"
    for j in range(len(a)):
        if a[j][i] != "?":
            if not hit:
                hit = True
                r = a[j][i]
            elif a[j][i] != r: return "?"
    return r

ar = list()
ans = list()
for snth in range(readint()):
    ar.append(input())
for i in range(len(ar[0])):
    ans.append(t(ar,i))
print(*ans,sep="")

	    					  	  		 	 		 		  	  	