#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
int pre[27], suf[27];
bool vis[27];
signed main()
{
    // freopen("ring.in", "r", stdin);
    // freopen("ring.out", "w", stdout);
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    memset(pre, -1, sizeof(pre));
    memset(suf, -1, sizeof(suf));
    bool f = 0;
    string s;
    for (int sb = 1; sb <= 2; sb++)
    {
        int n;
        cin >> n;
        while (n--)
        {
            cin >> s;

            for (int i = 0; i < int(s.size()); i++)
            {
                // cout << i << "\n";

                if (i > 0)
                {
                    pre[s[i - 1] - 'A'] = s[i] - 'A';
                    suf[s[i] - 'A'] = s[i - 1] - 'A';
                }
                vis[s[i] - 'A'] = 1;
            }
        }
    }
    s = "";
    for (int i = 0; i < 26; i++)
    {
        if (vis[i] && pre[i] == -1)
        {
            if (f)
            {
                cout << -1;
                return 0;
            }
            int u = i;
            while (u != -1)
            {
                s += u + 'A';
                u = suf[u];
            }
            f = 1;
        }
    }
    reverse(s.begin(),s.end());
    
    cout << s;
}