412C - Pattern - CodeForces Solution

n = int(input())
res_pattern = ''
for i in range(n):
    pattern = input()
    if i == 0:
        res_pattern = list(pattern)
        question_marks = [0] * len(res_pattern)
    for j in range(len(pattern)):
        if res_pattern[j] != pattern[j]:
            if res_pattern[j] == "?":
                res_pattern[j] = pattern[j]
            elif pattern[j] == "?":
                continue
            else:
                res_pattern[j] = "1"
        else:
            if res_pattern[j] == "?":
                question_marks[j] += 1

for k in range(len(res_pattern)):
    if res_pattern[k] == "1":
        res_pattern[k] = "?"
    if question_marks[k] == n:
        res_pattern[k] = "x"
print("".join(res_pattern))