#include <bits/stdc++.h>
using namespace std;
#define repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define rep(i,n) repl(i,0,n)
#define mp(a,b) make_pair((a),(b))
#define pb(a) push_back((a))
#define all(x) (x).begin(),(x).end()
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#define fi first
#define se second
#define dbg(x) cout<<#x" = "<<((x))<<endl
template<class T,class U> ostream& operator<<(ostream& o, const pair<T,U> &p){o<<"("<<p.fi<<","<<p.se<<")";return o;}
template<class T> ostream& operator<<(ostream& o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}

#define INF 21474836

int d[26][26];

int main(){
  fill(d[0], d[26], INF);
  vector<int> nxt(26,-1);

  int len;
  rep(_,2){
    len = 0;
    int n;
    cin>>n;
    rep(i,n){
      string s;
      cin>>s;
      len += s.size();
      rep(j,s.size()-1){
        d[s[j]-'A'][s[j+1]-'A'] = 1;
        nxt[s[j]-'A'] = s[j+1]-'A';
      }

      if(n==1 && len==1){
        cout << s << endl;
        return 0;
      }
    }
  }

  int n = 26;
  rep(i,n) d[i][i] = 0;
  rep(k,n) rep(i,n) rep(j,n) d[i][j] = min(d[i][j], d[i][k] + d[k][j]);

  rep(i,n) rep(j,n) if(d[i][j] == len-1){
    do {
      cout << (char)(i+'A');
      i = nxt[i];
    } while(i>=0);
    cout << endl;
    return 0;
  }
  cout << -1 << endl;

  return 0;
}