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() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int t;
  cin >> t;
  while (t--) {
    long long int n;
    cin >> n;
    long long int a[n];
    long long int ma = 0;
    long long int mi = 1e9;
    for (long long int i = 0; i < n; i++) {
      cin >> a[i];
      ma = max(ma, a[i]);
      mi = min(mi, a[i]);
    }
    if (ma == mi)
      cout << -1 << "\n";
    else {
      for (long long int i = 0; i < n; i++) {
        if (ma == a[i] && ma != a[i - 1]) {
          cout << i + 1 << "\n";
          break;
        }
        if (ma != a[i] && ma == a[i + 1]) {
          cout << i + 2 << "\n";
          break;
        }
      }
    }
  }
  return 0;
}
