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;
void solve();
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long t;
  cin >> t;
  while (t--) {
    solve();
    cout << "\n";
  }
  cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
  return 0;
}
void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  set<int> unq;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    unq.insert(a[i]);
  }
  if (unq.size() == 1)
    cout << -1;
  else
    cout << max_element(a.begin(), a.end()) - a.begin() + 1;
}
