#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

void fail() {
    std::cout << "-1\n";
    std::exit(0);
}

void solve() {
    std::vector<int> to(26, -1);
    std::vector<int> in(26, 0);
    std::vector<bool> used(26, false);

    for (int q = 0; q < 2; ++q) {
        int n;
        std::cin >> n;
        while (n--) {
            std::string s;
            std::cin >> s;
            for (char c : s) used[c - 'A'] = true;

            int m = s.length();
            for (int i = 0; i + 1 < m; ++i) {
                int u = s[i] - 'A', v = s[i + 1] - 'A';
                to[u] = v;
                ++in[v];
            }
        }
    }

    int r = -1;
    for (int v = 0; v < 26; ++v) {
        if (!used[v]) continue;
        if (in[v] == 0) {
            if (r != -1) fail();
            r = v;
        }
    }
    if (r == -1) fail();

    std::string ans;
    while (r != -1) {
        ans.push_back('A' + r);
        used[r] = false;
        r = to[r];
    }

    if (std::any_of(used.begin(), used.end(), [](auto b) { return b; })) fail();
    std::cout << ans << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}