#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  int N, M;
  vector<string> v, w;
  cin >> N;
  rep(i,N){
    string str;
    cin >> str;
    v.push_back(str);
  }
  cin >> M;
  rep(i,M){
    string str;
    cin >> str;
    w.push_back(str);
  }

  string retA = "";
  string retB = "";

  while(true){
    bool flg = false;
    rep(i,v.size()){
      if(v[i] != "") flg = true;
    }
    rep(i,w.size()){
      if(w[i] != "") flg = true;
    }
    if(!flg) break;
    
    if(retA.size() == retB.size()){
      int ii = -1, jj = -1;
      rep(i,N){
        rep(j,M){
          if(v[i][0] == w[j][0]){
            if(ii != -1){
              cout << -1 << endl;
              return 0;
            }
            ii = i;
            jj = j;
            break;
          }
        }
      }
      retA += v[ii]; v[ii] = "";
      retB += w[jj]; w[jj] = "";
    }else{
      if(retA.size() < retB.size()){
        int ii = -1;
        rep(i,v.size()){
          if(v[i][0] == retB[retA.size()]){
            ii = i;
            break;
          }
        }
        retA += v[ii]; v[ii] = "";
      }else{
        int jj = -1;
        rep(j,w.size()){
          if(w[j][0] == retA[retB.size()]){
            jj = j;
            break;
          }
        }
        retB += w[jj]; w[jj] = "";        
      }
    }
  }

  cout << retA << endl;
  return 0;
}