#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

set<char> used;
bool head[128];
char nxt[128];

string solve() {
  int h = 0;
  char x;
  for (char c = 'A'; c <= 'Z'; c++) {
    if (used.count(c) && head[c]) {
      x = c;
      ++h;
    }
  }

  if (h != 1) return "";

  string ret;
  while (x) {
    ret += x;
    x = nxt[x];
  }
  return ret;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  fill(head, head + 128, true);
  REP (i, 2) {
    int n;
    cin >> n;
    REP (j, n) {
      string s;
      cin >> s;
      for (int k = 0; k < s.length(); k++) {
        used.insert(s[k]);
        if (k > 0)
          head[s[k]] = false;
        if (k + 1 < s.length())
          nxt[s[k]] = s[k+1];
      }
    }
  }

  string ret = solve();
  cout << (ret.empty() ? "-1" : ret) << endl;
  
  return 0;
}