#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int int01;
  string str01, str02, result;

  cin >> int01;
  for (int i = 0; i < int01; i++) {
    cin >> str01;
    result += str01;
  }

  for (int i = 0; i < int01 - 1; i++) {
    cin >> str02;
    regex re(str02);
    result = regex_replace(result, re, "", regex_constants::format_first_only);
  }

  cout << result << endl;

  return 0;
}