import sys

n = int(input())
a = [input() for i in range(n)]
m = int(input())
b = [input() for i in range(m)]

s = set()
for x in a:
    s.update(x)
nxt = {}
for x in a:
    for i in range(len(x)-1):
        nxt[x[i]] = x[i+1]
        s.discard(x[i+1])
for x in b:
    for i in range(len(x)-1):
        nxt[x[i]] = x[i+1]
        s.discard(x[i+1])
if len(s) > 1:
    print(-1)
else:
    x = s.pop()
    while x in nxt:
        sys.stdout.write(x)
        x = nxt[x]
    print(x)