#include <iostream>
#include <algorithm>
using namespace std;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

int main(void) {
  int n; scanf("%d", &n);
  vector<string> s(n, string());
  for(int i : range(n)) {
    cin >> s[i];
    s[i] += 'z' + 1;
  }
  string t;
  for( ; ; ) {
    int p = -1;
    for(int i : range(n)) {
      if(s[i].size() > 1 && (p == -1 || s[p] > s[i])) { p = i; }
    }
    if(p < 0) { break; }
    t += s[p][0];
    s[p] = s[p].substr(1);
  }
  cout << t << endl;
  return 0;
}