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;
const int mod = 1e9 + 7;
void solve() {
  int n;
  cin >> n;
  int maxx = -mod;
  vector<int> arr(n);
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
    maxx = max(maxx, arr[i]);
  }
  for (int i = 0; i < n; i++) {
    if (i > 0 && arr[i] == maxx && arr[i] > arr[i - 1]) {
      cout << i + 1;
      return;
    }
    if (i < n && arr[i] == maxx && arr[i] > arr[i + 1]) {
      cout << i + 1;
      return;
    }
  }
  cout << "-1";
  return;
}
int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    solve();
    cout << "\n";
  }
  return 0;
}
