#include <iostream>
#include <vector>
#include <set>
using namespace std;
int main(){
  vector<int> a(26, -1);
  vector<int> a2(26, -1);
  set<int> b;
  for(int i = 0; 2 > i; i++){
    int n;cin>>n;
    for(int j = 0; n > j; j++){
      string s;cin>>s;
      for(int k = 0; s.size() > k; k++){
        if(k){
          a[s[k]-'A'] = s[k-1]-'A';
          a2[s[k-1]-'A'] = s[k]-'A';
        }
        b.insert(s[k]-'A');
      }
    }
  }
  string s = "";
  bool exist = false;
  for(int i = 0; 26 > i; i++){
    if(a[i] == -1 && b.count(i)){
      if(exist){
        cout << -1 << endl;
        return 0;
      }
      s.push_back(i+'A');
      int nw = i;
      while(a2[nw] != -1){
        nw = a2[nw];
        s.push_back(nw+'A');
      }
      exist = true;
    }
  }
  cout << s << endl;
}