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

template<class T> istream& operator >> (istream& is, vector<T>& vec) {
    for(T& x : vec) is >> x;
    return is;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n;
    vector<string> a(n);
    cin >> a >> m;
    vector<string> b(m);
    cin >> b;
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    if(n == 1 || m == 1){
        cout << (n == 1 ? a[0] : b[0]) << '\n';
        return 0;
    }
    for(auto &&s : a){
        if(binary_search(b.begin(), b.end(), s)){
            cout << -1 << '\n';
            return 0;
        }
    }
    string sa, sb;
    int S1 = 0, S2 = 0, cnt = 0, cnt2 = 0;
    for(int i = 0; i < n; i++) S1 |= 1 << a[i][0] - 'A';
    for(int i = 0; i < m; i++) S2 |= 1 << b[i][0] - 'A';
    S1 &= S2;
    if(__builtin_popcount(S1) >= 2){
        cout << -1 << '\n';
        return 0;
    }
    for(int i = 0; i < n; i++){
        if((S1 >> a[i][0] - 'A') & 1) sa += a[i];
        cnt += a[i].size();
    }
    for(int i = 0; i < m; i++){
        if((S1 >> b[i][0] - 'A') & 1) sb += b[i];
        cnt2 += b[i].size();
    }
    if(cnt != cnt2){
        cout << -1 << '\n';
        return 0;
    }
    while(sa.size() < cnt || sb.size() < cnt){
        if(sa.size() == sb.size()){
            cout << -1 << '\n';
            return 0;
        }
        if(sa.size() < sb.size()){
            int pre = sa.size(), siz = sb.size() - sa.size();
            string su = sb.substr(sb.size() - siz, 1);
            for(int i = 0; i < n; i++){
                if(a[i].substr(0, 1) == su){
                    sa += a[i];
                    break;
                }
            }
            if(sa.size() == pre){
                cout << -1 << '\n';
                return 0;
            }
        }else{
            int pre = sb.size(), siz = sa.size() - sb.size();
            string su = sa.substr(sa.size() - siz, 1);
            for(int i = 0; i < m; i++){
                if(b[i].substr(0, 1) == su){
                    sb += b[i];
                    break;
                }
            }
            if(sb.size() == pre){
                cout << -1 << '\n';
                return 0;
            }
        }
    }
    cout << (sa == sb ? sa : "-1") << '\n';
}