#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin >> n;

    map<string, int> db;

    for(int i = 0; i < n; i++){
        string s;
        cin >> s;

        sort(s.begin(), s.end());

        db[s]++;
    }

    for(auto [a, x] : db){
        if(x % 2 == 1){
            cout << a << "\n";
            break;
        }
    }
}