/* -*- coding: utf-8 -*-
 *
 * 517.cc: No.517 壊れたアクセサリー - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 26;

/* typedef */

/* global variables */

bool used[MAX_N];
int prvs[MAX_N], nxts[MAX_N];

/* subroutines */

/* main */

int main() {
  memset(prvs, -1, sizeof(prvs));
  memset(nxts, -1, sizeof(nxts));

  for (int i = 0; i < 2; i++) {
    int n;
    cin >> n;

    for (int j = 0; j < n; j++) {
      string s;
      cin >> s;

      for (int k = 0; k < s.size(); k++) {
	int t = s[k] - 'A';
	used[t] = true;
	if (k > 0) {
	  int u = s[k - 1] - 'A';
	  prvs[t] = u;
	  nxts[u] = t;
	}
      }
    }
  }

  int top = -1;
  for (int i = 0; i < 26; i++)
    if (used[i] && prvs[i] < 0) {
      if (top >= 0) {
	puts("-1");
	return 0;
      }
      top = i;
    }

  for (int i = top; i >= 0; i = nxts[i]) putchar(i + 'A');
  putchar('\n');
  return 0;
}