#include <bits/stdc++.h>
using namespace std;

list<string> n,m;
string ns,ms;

bool get(char c, bool isn) {
    if (isn) for (auto nitr = n.begin(); nitr != n.end(); ++nitr) {
        if ((*nitr)[0] == c) { ns += *nitr; n.erase(nitr); break;}
    } else for (auto mitr = m.begin(); mitr != m.end(); ++mitr) {
        if ((*mitr)[0] == c) { ms += *mitr; m.erase(mitr); break;}
    }
}

bool init() {
    int i = 0;
    bool flag = false;
    for (auto nitr = n.begin(); nitr != n.end(); ++nitr) {
        for (auto mitr = m.begin(); mitr != m.end(); ++mitr) {
            if ((*nitr)[0] == (*mitr)[0]) {
                if (flag) return false;
                ns += *nitr;
                nitr = n.erase(nitr); nitr--;
                ms += *mitr;
                mitr = m.erase(mitr); mitr--;
                flag = true;
            }
        }
    }
    return true;
}

int main(void) {
    int N,M;
    string s;
    cin >> N;
    for (int i = 0; i < N; i++) {cin >> s; n.push_back(s);}
    cin >> M;
    for (int i = 0; i < M; i++) {cin >> s; m.push_back(s);}
    if(!init()) { cout << -1 << endl; return 0;}
    while(ns != ms) {
        if (ns.size() > ms.size()) get(ns[ms.size()], false);
        else if (ns.size() < ms.size()) get(ms[ns.size()], true);
    }
    cout << ns << endl;
    return 0;
}