1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  int n;
  while (t--) {
    cin >> n;
    set<int> se;
    while (n--) {
      int i;
      cin >> i;
      se.insert(i);
    }
    if (se.size() >= 2) {
      cout << *se.rbegin() << endl;
    } else
      cout << -1 << endl;
  }
}
