from calendar import c


N = int(input())
A = [input() for _ in range(N)]
M = int(input())
B = [input() for _ in range(M)]
l = 0
for i in range(N):
    l += len(A[i])
res = 0
for i in range(N):
    for j in range(M):
        if A[i][0] == B[j][0]:
            a, b = [0]*l, [0]*l
            id_a, id_b = 0, 0
            sa, sb = set(), set()
            sa.add(i);sb.add(j)
            for k in range(len(A[i])):
                a[id_a] = ord(A[i][k])
                id_a += 1
            for k in range(len(B[j])):
                b[id_b] = ord(B[j][k])
                id_b += 1
            while id_a<l or id_b<l:
                if id_a==id_b:
                    f = False
                    for ii in range(N):
                        for jj in range(M):
                            if A[ii][0]==B[jj][0] and ii not in sa and jj not in sb:
                                sa.add(ii);sb.add(jj)
                                for kk in range(len(A[ii])):
                                    a[id_a] = ord(A[ii][kk])
                                    id_a += 1
                                for kk in range(len(B[jj])):
                                    b[id_b] = ord(B[jj][kk])
                                    id_b += 1
                                f = True
                                break
                        if f:
                            break
                elif id_a>id_b:
                    ss = chr(a[id_b])
                    for ii in range(M):
                        if ss == B[ii][0] and ii not in sb:
                            sb.add(ii)
                            for kk in range(len(B[ii])):
                                b[id_b] = ord(B[ii][kk])
                                id_b += 1
                            break
                else:
                    ss = chr(b[id_a])
                    for ii in range(N):
                        if ss == A[ii][0]:
                            sa.add(ii)
                            for kk in range(len(A[ii])):
                                a[id_a] = ord(A[ii][kk])
                                id_a += 1
                            break
            for ll in range(l):
                if a[ll] != b[ll]:
                    break
            else:
                res += 1
                ans = a.copy()
if res == 1:
    ret = ''
    for i in ans:
        ret += chr(i)
    print(ret)
else:
    print(-1)