import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


n = int(input())
a = [input() for _ in range(n)]
m = int(input())
b = [input() for _ in range(m)]
ns = [[] for _ in range(26)]
rns = [[] for _ in range(26)]
ds = [0]*26
seen = [0]*26
for s in a+b:
    for i in range(len(s)):
        ci = ord(s[i]) - ord("A")
        seen[ci] = 1
        for j in range(i):
            cj = ord(s[j]) - ord("A")
            ns[cj].append(ci)
            rns[ci].append(cj)
            ds[cj] += 1
            seen[ci] = seen[cj] = 1

def cycle(rns, ds):
    """出次数0の頂点を削除しつづける
    DAGならTPS順序も求まる
    rns: 逆辺の隣接リスト
    ds: もとのグラフにおける出次数
    返り値
    vs: 除かれた頂点
    done: 除いたフラグ
    """
    from collections import deque
    q = deque()
    n = len(rns)
    done = [False] * n
    ok = 1
    for u in range(n):
        if ds[u]==0:
            if not seen[u]:
                done[u] = True
                continue
            q.append(u)
            done[u] = True
    vs = []
    while q:
#         print([chr(ord("A")+v) for v in q])
        if len(q)>=2:
            ok = 0
        u = q.popleft()
        vs.append(u)
        for v in rns[u]:
            if done[v]:
                continue
            ds[v] -= 1
            if ds[v]==0:
                done[v] = True
                q.append(v)
    return vs,done,ok
vs,done,ok = cycle(rns,ds)
if all(done):
    if ok:
        ans = "".join(map(chr, ((ord("A")+v) for v in vs)))[::-1]
    else:
        ans = -1
else:
    ans = -1
print(ans)