#include <iostream>
#include <bits/stdc++.h>
using ll = long long;
using namespace std;

int main()
{
    ll n; cin >> n;
    vector<string> v(n);
    for (ll i = 0; i < n; i++){
        cin >> v[i];
        sort(v[i].begin(), v[i].end());
    }
    sort(v.begin(), v.end());
    ll even = 1, flag = 0;
    string now = v[0];
    string ans;
    for (ll i = 1; i < n; i++){
        if (now == v[i]){
            even++; continue;
        }
        else if (even % 2 != 0){
            ans = v[i-1]; flag = 1; even = 0; break;
        }
    }
    if (flag == 0) ans = v[n-1];
    cout << ans;
    return 0;
}