import io
import sys
from collections import defaultdict, deque, Counter
from itertools import permutations, combinations, accumulate
from heapq import heappush, heappop
from bisect import bisect_right, bisect_left
from math import gcd
import math

_INPUT = """\
6
3
rock
scissors
paper
2
file
life
5
one
plus
one
equals
two
"""

def input():
  return sys.stdin.readline()[:-1]

def solve(test):
  N=int(input())
  S=[input() for _ in range(N)]
  d=defaultdict(int)
  for s in S:
    d[tuple([s.count(chr(i+ord('a'))) for i in range(26)])]+=1
  flg=0
  for k in d:
    if flg==1: break
    if d[k]==1:
      for i in range(26):
        if flg==1: break
        flg2=0
        for j in range(26):
          if flg==1: break
          if i==j or k[j]==0: continue
          if tuple([k[l]+1 if l==i else k[l]-1 if l==j else k[l] for l in range(26)]) in d:
            flg2=1
            break
        if flg2==0:
          flg=1
          ans=tuple([k[l]+1 if l==i else k[l] for l in range(26)])
  if flg==1: print(''.join([chr(i+ord('a'))*ans[i] for i in range(26)]))
  else: print(-1)

def random_input():
  from random import randint,shuffle
  N=randint(1,10)
  M=randint(1,N)
  A=list(range(1,M+1))+[randint(1,M) for _ in range(N-M)]
  shuffle(A)
  return (" ".join(map(str, [N,M]))+"\n"+" ".join(map(str, A))+"\n")*3

def simple_solve():
  return []

def main(test):
  if test==0:
    solve(0)
  elif test==1:
    sys.stdin = io.StringIO(_INPUT)
    case_no=int(input())
    for _ in range(case_no):
      solve(0)
  else:
    for i in range(1000):
      sys.stdin = io.StringIO(random_input())
      x=solve(1)
      y=simple_solve()
      if x!=y:
        print(i,x,y)
        print(*[line for line in sys.stdin],sep='')
        break

#0:提出用、1:与えられたテスト用、2:ストレステスト用
main(0)