#include<bits/stdc++.h>
using namespace std;
int main() {
int n1,n2;
list l1;
list l2;
cin>>n1;
for(int i=0; i<n1; i++){
int x; cin>>x;
l1.push_back(x);
}
cin>>n2;
for(int i=0; i<n2; i++){
int x; cin>>x;
l2.push_back(x);
}
int ans=-1;
while(l1.back()==l2.back()){
ans=l1.back();
l1.pop_back();
l2.pop_back();
}
cout<<ans;
return 0;
}