from collections import deque

N=int(input())
A=[input() for i in range(N)]

M=int(input())
B=[input() for i in range(M)]

AQ=deque()
BQ=deque()
ANS=[]

while (A and B) or AQ or BQ:
    if AQ and BQ:
        if AQ[0] and BQ[0]:
            s=AQ.popleft()
            BQ.popleft()
            ANS.append(s)
            continue
        else:
            print(-1)
            exit()

    if AQ:
        s=AQ[0]
        ind=-1
        for i in range(len(B)):
            if B[i][0]==s:
                ind=i
                break

        if ind==-1:
            print(-1)
            exit()
        else:
            BQ=deque(B[ind])
            B.pop(ind)
            continue

    if BQ:
        s=BQ[0]
        ind=-1
        for i in range(len(A)):
            if A[i][0]==s:
                ind=i
                break

        if ind==-1:
            print(-1)
            exit()
        else:
            AQ=deque(A[ind])
            A.pop(ind)
            continue

    SA=set()
    SB=set()

    for a in A:
        SA.add(a[0])
    for b in B:
        SB.add(b[0])

    SS=SA & SB

    if len(SS)==1:
        s=list(SS)[0]

        for i in range(len(A)):
            if A[i][0]==s:
                ind=i
                break
        AQ=deque(A[ind])
        A.pop(ind)

        for i in range(len(B)):
            if B[i][0]==s:
                ind=i
                break
        BQ=deque(B[ind])
        B.pop(ind)
    else:
        print(-1)
        exit()

    
        
            
print("".join(ANS))