#include<iostream>
using namespace std;
#include<vector>
#include<algorithm>
int main(){
int a;
int e,k,kk=0,kkk=0;
vector<int>q;
cin>>a;
for(int i=0;i<a;i++)
{cin>>e;
q.push_back(e);
}
sort(q.begin(),q.end());
q.insert(q.begin(),0);
k=q[a/2+1];
for(int i=1;i<=a;i++){
if(q[i]<k)
kk++;
if(q[i]>k)
kkk++;
}
if(kk==kkk)
cout<<q[kk+1];
else
cout<<"-1";
return 0;
}
using namespace std;
#include<vector>
#include<algorithm>
int main(){
int a;
int e,k,kk=0,kkk=0;
vector<int>q;
cin>>a;
for(int i=0;i<a;i++)
{cin>>e;
q.push_back(e);
}
sort(q.begin(),q.end());
q.insert(q.begin(),0);
k=q[a/2+1];
for(int i=1;i<=a;i++){
if(q[i]<k)
kk++;
if(q[i]>k)
kkk++;
}
if(kk==kkk)
cout<<q[kk+1];
else
cout<<"-1";
return 0;
}