#include<bits/stdc++.h>
using namespace std;
int main(){int N;cin>>N;string S[N];for(int i=0;i<N;i++)cin>>S[i];string T;int j=0;for(int i=0;i<N-1;i++){cin>>T;if(S[j]!=T){cout<<S[j]<<endl;return 0;}else{j++;}}cout<<S[j]<<endl;}