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

int main(){
    int N;
    cin >> N;
    multiset<string> S;
    for (int i = 0; i < N; i++){
        string s;
        cin >> s;
        S.insert(s);
    }
    for (int i = 1; i < N; i++){
        string s;
        cin >> s;
        S.erase(S.find(s));
    }
    cout << *S.begin() << endl;
}