#include <bits/stdc++.h>

int main() {

  std::string str[64];
  int N;
  int times = 0;
  std::vector<char> v;
  std::string t;
  
  std::cin >> N;
  for(int i = 0; i < N; ++i) {
    std::cin >> t;
    t += "{";
    str[i] = t;
    times += str[i].size()-1;
  }
  
  std::sort(str, str+N);
  for(int i = 0; i < times; ++i) {
    v.push_back(str[0][0]);

    for(int j = 1; j < str[0].size(); ++j) {
      str[0][j-1] = str[0][j];
    }
    str[0][str[0].size()-1] = '\0';
    str[0] = str[0].c_str();
    
    for(int j = 1; j < N; ++j) {
      if( str[j-1] > str[j] && str[j].size() != 1 ) {
	std::swap(str[j-1], str[j]);
      }
      else {
	break;
      }
    }

  }
  v.push_back('\0');
  
  std::cout << &v[0] << std::endl;

  return 0;
}