#include using namespace std; #define rep(i,n) REP(i,0,n) #define REP(i,s,e) for(int i=(s); i<(int)(e); i++) #define repr(i, n) REPR(i, n, 0) #define REPR(i, s, e) for(int i=(int)(s-1); i>=(int)(e); i--) #define pb push_back #define all(r) r.begin(),r.end() #define rall(r) r.rbegin(),r.rend() #define fi first #define se second typedef long long ll; typedef vector vi; typedef vector vl; typedef pair pii; typedef pair pll; const int INF = 1e9; const ll MOD = 1e9 + 7; double EPS = 1e-8; int main(){ int n; cin >> n; vector s(n); rep(i, n) cin >> s[i]; priority_queue,greater > q; rep(i, n) q.push(s[i]); string ans; while(!q.empty()) { auto t = q.top(); q.pop(); ans += t[0]; if(t.size() > 1) q.push(t.substr(1)); } cout << ans << endl; return 0; }