import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
n = ni()
s = [input()for i in range(n)]

a = []
for i in range(n):
    if s[i][i] == "a":
        a.append("b")
    else:
        a.append("a")
print("".join(a))